Reflection-type liquid crystal display device and fabrication process thereof

ABSTRACT

A reflection-type liquid crystal display device includes a first substrate, a second substrate facing the first substrate and carrying projections and depressions, a reflective electrode on the second substrate so as to cover the projections and depressions and in electrical contact with a switching device provided on the second substrate via a contact hole, and a negative liquid crystal layer between the first and second substrates, wherein the contact hole is disposed centrally to the reflection electrode and a structure controlling alignment of liquid crystal molecules in the liquid crystal layer is disposed so as to overlap the contact hole viewed in a direction perpendicular to the second substrate.

CROSS-REFERENCE TO RELATED APPLICATION.

[0001] The present application is based on Japanese priority applicationNo.2001-377791 filed on Dec. 11, 2001, the entire contents of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention generally relates to reflection-type liquidcrystal display devices used in a low-power apparatuses such as portableterminals.

[0003] A reflection-type liquid crystal display device is a liquidcrystal display device that achieves display of images by incorporatingenvironmental light such as interior illumination light or sunlight andcausing the same to reflect toward an observer by means of a reflector.

[0004] Because of the operational principle, the reflection-type liquidcrystal display device does not need a backlight and has an advantageousfeature of low power consumption. Thus, reflection-type liquid crystaldisplay devices are used extensively for portable terminals.

[0005] In order to achieve bright and clear representation of images ina reflection-type liquid crystal display device, it is necessary todesign the liquid crystal display device such that as much environmentallight as possible is incorporated and reflected toward the observer inthe white representation mode and that the reflection of theincorporated light toward the observer is suppressed as much as possiblein the black representation mode.

[0006] Thus, there is a proposal of a reflection-type liquid crystaldisplay device that uses a phase-change type guest-host (GH) mode (D. L.White and G. N. Taylor, J. Appl. Phys. 45, pp.4718, 1974). Because aGH-mode reflection-type liquid crystal display device does not require apolarizer, there is a distinct advantage in such a GH-modereflection-type liquid crystal display device that a brightrepresentation is achieved in the white representation mode.

[0007] On the other hand, a GH-mode liquid crystal display device has adrawback in that a bright representation is obtained also in the backrepresentation mode and the contrast ratio is limited to the range of5-6.

[0008] Meanwhile, there is a proposal of a reflection-type liquidcrystal display device of a twisted nematic mode that uses a singlepolarizer as in the Japanese Laid-Open Patent Publication 6-11711.

[0009] This conventional reflection-type liquid crystal display deviceis basically a horizontally oriented liquid crystal device in whichliquid crystals having a positive dielectric anisotropy are twisted. Inthe foregoing conventional reflection-type liquid crystal displaydevice, the incoming environmental light is converted to a linearpolarization light by a polarizer, and the linearly polarized light thusobtained is passed through a liquid crystal layer or a phasecompensation film having a ¼-wavelength retardation, so that there isachieved a 90 degree angle of polarization plane between the incidentlight passed through the polarizer and the reflection light returning tothe polarizer.

[0010] Thus, in this conventional liquid crystal display device, theblack representation is achieved by absorbing the rotated reflectionlight by the polarizer. Because of the use of the polarizer, theforegoing conventional liquid crystal display device can provide onlyabout 40% of brightness in the while representation mode as comparedwith the case of the GH-mode liquid crystal display device. However, theliquid crystal display device can achieve a contrast ratio of 12-14 inview of efficient absorption of the light in the black representationmode.

[0011] Further, there is a proposal of improving the contrast ratio in aTN-mode liquid crystal display device by way of compensating for theblack representation, by reducing the amount of retardation of the phasecompensation film by the magnitude of the residual retardation of theliquid crystal layer. See Japanese Laid-Open Patent Publication11-311784. With this, the contrast ratio is improved to about 16-18.

[0012] In a reflection-type liquid crystal display device, thevisibility of representation is defined by brightness and contrastratio. Thus, a high visibility is achieved even in the case of lowcontrast ratio when the representation is bright. When therepresentation is dark, on the other hand, a large contrast ratio isrequired. See The Journal of the Institute of Television Engineers ofJapan, Vol.50, No.8, pp.1091-1095 (1996).

[0013] A contrast ratio of about 12 is needed in order to realize thevisibility comparable to that of a GH-mode liquid crystal display deviceby using a liquid crystal display device having a single polarizer, thelatter liquid crystal display device can provide the brightness of only40% of the brightness of a GH-mode liquid crystal display device. Byusing the technology noted in the above reference, it becomes possibleto achieve a contrast ratio of 16-18 by using a T-N mode liquid crystaldisplay device.

[0014] Because of the foregoing reason, and further in view of betterreliability, a TN-mode liquid crystal display device having a singlepolarizer is used widely in these days for a reflection-type liquidcrystal display device.

[0015] In a TN-mode liquid crystal display device having a singlepolarizer, it should be noted that the upper and lower substrates aresubjected to rubbing processing in different directions so as to realizethe twisted structure in the liquid crystal layer. As a consequence, theanchoring direction of the liquid crystal layer is not coincident in theupper and lower substrates.

[0016] Because of this, the technology of the foregoing JapaneseLaid-Open Patent Publication 11-311784 sets the retardation axis of thephase compensation film at the angle intermediate between the upper andlower anchoring directions so as to compensate for the synthetic vectorof the upper and lower anchoring directions. However, this constructioncannot compensate for the residual retardation of the liquid crystallayer at the upper and lower substrates individually and thecompensation for the black representation remains incomplete.

[0017] Meanwhile, there is a proposal of a reflection-type liquidcrystal display device of vertically aligned (VA)-mode that uses asingle polarizer (See Japanese Laid-Open Patent Publication 6-337421).

[0018] In such a VA-mode liquid crystal display device, the On and Offoperation is just the opposite as in the case of a TN-mode liquidcrystal display device. On the other hand, the operational features of:converting the incoming environmental light to linearly polarized lightby the polarizer; rotating the polarization plane of the linearlypolarized light thus obtained by 90 degrees by using a liquid crystallayer or a phase compensation film having a retardation of about ¼wavelength of visible light; and causing the polarizer to absorb therotated linearly polarized light in the black representation mode, areidentical between the foregoing VA-mode liquid crystal display deviceand the TN-mode liquid crystal display device.

[0019] On the other hand, the VA-mode reflection-type liquid crystaldisplay device is advantageous in the point that there remains no liquidcrystal layer causing anchoring at the liquid crystal/substrateinterface in the black representation mode contrary to the case of theTN-mode liquid crystal display device because of the fact that the blackrepresentation mode is achieved in the VA-mode reflection-type liquidcrystal display device in the state no voltage is applied to the liquidcrystal layer. Thereby, the contrast ratio of image representation isimproved significantly.

[0020] In this way, the VA-mode reflection-type liquid crystal displaydevice has an advantageous feature of high contrast ratio and excellentvisibility.

[0021] On the other hand, there still exist problems to be solved insuch a VA-mode reflection-type liquid crystal display deviceparticularly with regard to the control of alignment of the liquidcrystal molecules.

[0022] More specifically, a VA-mode liquid crystal display devicegenerally uses a vertical alignment film, while the performance of sucha vertical alignment film may be degraded seriously when subjected to arubbing process. For example, there may be caused defective display ofimages such as uneven brightness extending in the form of streaksBecause of this reason, there is a need of achieving alignment controlof liquid crystal molecules in a VA-mode liquid crystal display deviceby means other than rubbing.

[0023] In the Japanese Laid-Open Patent Publication 10-301112, forexample, the alignment control of the liquid crystal molecules isachieved by providing a slit extending obliquely in a reflectionelectrode on the opposite substrate, such that there is induced anoblique electric field between the upper and lower substrates uponapplication of a voltage.

[0024] This technology, on the other hand, has a drawback in that theoverall reflectivity of the pixels is reduced because the part of theliquid crystal layer located immediately on the slit does not undergoswitching and the visibility of the image representation is not verymuch improved even when the contrast ratio is improved.

[0025] Thus, there has been a need of improving the contrast ratiowithout sacrificing the reflectivity in a VA-mode liquid crystal displaydevice.

[0026] Meanwhile, a reflection-type liquid crystal display devicegenerally has a problem of the visibility influenced heavily by theoptical environment such that the visibility of the images is degradedseriously in the dark optical environment. With this respect, atransmission-type liquid crystal display device having a backlightprovides far superior visibility. On the other hand, a transmission-typeliquid crystal display device suffers from the problem of poorvisibility in the bright optical environment in that the obtainedvisibility is inferior to the visibility achieved by the reflection-typeliquid crystal display device.

[0027] Thus, in order to improve the foregoing problems, there has beenproposals such as using a front light in combination with areflection-type liquid crystal display device, or a reflection-typeliquid crystal display device having a semi-transparent reflection film.

[0028] The approach of using a front light, however, suffers from theproblem in that the contrast ratio achieved in the dark opticalenvironment may be inferior to the contrast ratio of the direct-viewtype transmission-type liquid crystal display device. In the brightoptical environment, on the other hand, there may arise another problemin that the representation becomes dark as compared with theconventional reflection-type liquid crystal display device because ofthe existence of the front light.

[0029] In the case of using a semi-transparent film, a metal thin filmis generally used for this purpose. However, a metal thin film has alarge absorption coefficient and has a problem in the efficiency ofutilization of light. Further, the metal thin film suffers from theproblem of conspicuous variation of transmittance because of thein-plane variation of film thickness. It should be noted that such ametal thin film is generally provided by a thin Al film having athickness of about 30 nm. Currently, it is difficult for form a metalthin film with uniform thickness over a wide display area.

[0030] In order to eliminate the foregoing problem, there has been aproposal in the Japanese Laid-Open Patent Publication 11-281972 in whichthere is provided a transparent window by means of a transparentelectrode such as ITO (In₂O₃.SnO₂) at the central part of the pixels.According to this conventional proposal, the foregoing problems areeliminated and it became possible to construct areflection-transmission-type liquid crystal display device.

[0031] On the other hand, the foregoing conventional proposal of thereflection-transmission-type liquid crystal display device has neededformation of projections and depressions on a planarized film andformation of a step in the transmission region by forming a hole.Further, the foregoing technology requires formation of both thetransparent electrode (ITO) and the reflection electrode (Al) andfurther the formation of a barrier metal film for preventingelectrolytic corrosion, which may be caused at the contacting part ofthe Al pattern and the ITO pattern. Thus, the fabrication process of theliquid crystal display device is complex and the cost of fabricationcould not be reduced.

[0032] Further, the conventional reflection-type liquid crystal displaydevice, relying upon the principle of optical switching caused byretardation of the liquid crystal layer, has to be designed to have acell thickness of ½ of the wavelength of the visible light in thetransmission region and a cell thickness of ¼ of the wavelength of thevisible light in the reflection region. However, such a structure hasbeen difficult to produce.

SUMMARY OF THE INVENTION

[0033] Accordingly, it is a general object of the present invention toprovide a novel and useful liquid crystal display device wherein theforegoing problems are eliminated.

[0034] Another and more specific object of the present invention is toprovide a reflection-type liquid crystal display device and fabricationprocess thereof capable of realizing a high reflectivity and highcontrast ratio.

[0035] Another object of the present invention is to provide areflection-transmission-type liquid crystal display device capable ofbeing produced with low cost and having excellent characteristics.

[0036] Another object of the present invention is to provide areflection-type liquid crystal display device, comprising:

[0037] a first substrate;

[0038] a second substrate disposed so as to face said first substrate,said second substrate carrying projections and depressions thereon;

[0039] a reflective electrode provided on said second substrate so as tocover said projections and depressions in electrical contact with aswitching device provided on said second substrate via a contact hole;and

[0040] a liquid crystal layer provided between said first and secondsubstrates, said liquid crystal layer having a negative dielectricanisotropy,

[0041] wherein said contact hole is disposed centrally to saidreflection electrode, and

[0042] wherein a structure controlling alignment of liquid crystalmolecules in said liquid crystal layer is disposed so as to overlap saidcontact hole when said second substrate is viewed in a directionperpendicular thereto.

[0043] According to the present invention, the degradation ofreflectivity, caused by the foregoing structure for controlling thealignment of the liquid crystal molecules, is minimized by forming thestructure in correspondence to the contact hole where there is caused adegradation of reflectivity because of the absence of the projectionsand depressions.

[0044] By forming the contact hole at the central part of the pixelelectrode so as to avoid the peripheral part in which the liquid crystalmolecules are tilted in the inward direction as a result of the actionof the oblique electric field, it becomes possible to define foursectors in each pixel electrode by two hypothetical diagonal linescrossing at the center where the foregoing structure is provided.

[0045] In such a construction, the liquid crystal molecules of differentalignment directions interfere with each other on the foregoing diagonallines, resulting in an offset in the molecular alignment direction. Onthe other hand, such a construction can successfully eliminate theazimuth dependence of the reflection light by converging the lightincoming to the liquid crystal layer to a circularly polarized light byproviding a phase compensation film having a retardation of about ¼ ofthe visible wavelength. Thereby, the degradation of reflectivity causedby deviation of the azimuth angle of the reflected light is successfullysuppressed.

[0046] Another object of the present invention is to provide a method offabricating a reflection-type liquid crystal display device comprising afirst substrate, a second substrate provided so as to face said firstsubstrate, said second substrate carrying thereon projections anddepressions having a reflectivity, a liquid crystal layer having anegative dielectric anisotropy provided between said first and secondsubstrates, and an optically polymerized polymer structure providedbetween said first and second substrates, said method comprising thesteps of:

[0047] causing optical polymerization of a compound constituting saidpolymer structure by irradiating light perpendicularly to said secondsubstrate and causing reflection of said light by said projections anddepressions in an in-plane direction of said second substrate;

[0048] said step of causing optical polymerization is conducted byproviding an in-plane directivity to the light reflected by saidprojections and depressions by a optimizing a shape of said projectionsand depressions, such that said optical polymerization is conducted in adirection corresponding to said in-plane directivity.

[0049] According to the present invention, it becomes possible tostabilize the alignment of the liquid crystal molecules by the use ofthe optically polymerized polymer structure formed in the liquid crystallayer at the time of application of a control voltage. In such anoptically polymerized polymer structure, the polymer chains can beformed in an arbitrary direction by conducting optical irradiation inthe state of applying a voltage to the optically polymerized polymersdispersed in the liquid crystal layer. Thereby, the alignment of theliquid crystal molecules at the time of application of the voltage isstabilized because of the affinity between the polymer chain and theliquid crystal molecules.

[0050] In the present invention, it should be noted that the projectionsand depressions are designed so as to reflect the obliquely incominglight toward the observer. When light is directed perpendicularly insuch a substrate, the light is reflected by the projections anddepressions in the in-plane direction of the substrate. Thus, by causingthe optically polymerizable polymer by the light directedperpendicularly to the substrate surface, it becomes possible to form apolymer chain corresponding to the directivity of reflection. As theliquid crystal molecules are aligned along the optically polymerizablepolymer thus formed, the alignment of the liquid crystal molecules isstabilized.

[0051] Another object of the present invention is to provide areflection-type liquid crystal display device, comprising:

[0052] a first substrate;

[0053] a second substrate disposed so as to face said first substrate;

[0054] a liquid crystal layer having a negative dielectric anisotropydisposed between said first and second substrates; and

[0055] a vertical alignment film formed on a surface of said firstsubstrate and a surface of said second substrate,

[0056] wherein said alignment film contains a vertical alignmentcomponent with a proportion of 25% or more with regard to total diaminecomponents.

[0057] According to the present invention, it becomes possible toachieve a sufficient contrast ratio even in the case the substrate ofthe reflection-type liquid crystal display device is the one having areflective projections and depressions thereon, by setting theproportion of the vertical alignment component in the vertical alignmentfilm to be 25% or more with respect to the entire diamine components.

[0058] Another object of the present invention is to provide areflection-type liquid crystal display device, comprising:

[0059] a first substrate;

[0060] a second substrate disposed so as to face said second substrate,said second substrate carrying thereon projections and depressionshaving a reflectivity;

[0061] a liquid crystal layer having a negative dielectric anisotropydisposed between said first and second substrates; and

[0062] a polarizer disposed at an outer side of said first substratesuch that an absorption axis of said polarizer extends generallyparallel to a direction in which a reflection intensity caused by saidprojections and depressions becomes maximum.

[0063] According to the present invention, it becomes possible toimprove the contrast ratio of the liquid crystal display device bysetting the direction of the absorption axis of the polarizer to begenerally coincident with the direction in which the reflectionintensity of the reflection from the projections and depressions becomesmaximum. The present invention utilizes the phenomenon that the opticalabsorption efficiency of the polarizer is higher in the direction of theoptical absorption axis, in which direction the polarizing componentssuch a iodine or dichroic dyes are aligned, than other directions. Byaligning the direction of the polarizer in which the efficiency ofoptical absorption is maximum to be coincident with the direction inwhich the reflection from the depressions and projections is thestrongest, the present invention suppresses the brightness at the timeof the black representation mode further.

[0064] Of course, such a setting of the absorption axis of the polarizerresults in a decrease of brightness also in the white representationmode. In the case of the reflection-type liquid crystal display devicehaving the reflective projections and depressions thereon, on the otherhand, actual degradation of brightness in the white representation modeis suppressed minimum because the light from every direction isreflected in the direction perpendicular to the substrate. Thus, thepresent invention can achieve the improvement of contrast ratio withoutsacrificing the brightness of the reflection-type liquid crystal displaydevice.

[0065] Another object of the present invention is to provide areflection-type liquid crystal display device, comprising:

[0066] a first substrate;

[0067] a second substrate disposed so as to face said first substrate,said second substrate carrying projections and depressions having areflectivity;

[0068] a liquid crystal layer having any of positive or negativedielectric anisotropy provided between said first and second substrates;and

[0069] a polarizer disposed at an outer side of said first substrate,

[0070] an optical phase compensation film disposed between said firstsubstrate and said polarizer, said optical phase compensation filmhaving a negative dielectric anisotropy in a direction perpendicular toa plane of said first substrate,

[0071] said optical phase compensation film having a retardationdf{(n_(x)+n_(y))/2−n_(z)} so as to satisfy the relationship

0.4≦[df{(n _(x) +n _(y))/2−n _(z)}]/(dlcΔn)≦0.7,

[0072] wherein n_(x), n_(y) and n_(z) are refractive indices of saidoptical phase compensation film respectively in an x-direction, ay-direction and a z-direction, dlc is the thickness of said liquidcrystal layer, and Δn is a refractive index difference between anextraordinary ray and an ordinary ray in the liquid crystal layer.

[0073] According to the present invention, it is possible to compensatefor the leakage light formed at the time of the black representationmode substantially completely in a reflection-type liquid crystaldisplay device having a substrate carrying thereon reflectiveprojections and depressions for the case in which the foregoingprojections and depressions are optimized so as to incorporate as muchenvironmental light as possible within a limitation that there is causedno interface reflection.

[0074] Another object of the present invention is to provide areflection-transmission-type liquid crystal display device, comprising:

[0075] a first substrate;

[0076] a second substrate provided so as to face said first substrate;

[0077] a transparent electrode provided on a surface of said firstsubstrate facing said second substrate;

[0078] a reflection electrode provided on a surface of said secondsubstrate facing said first substrate, said reflection electrode havingan opening;

[0079] a scattering layer provided between said first and secondsubstrates, said scattering layer including therein a liquid crystallayer and changing an optical state thereof between a scattering stateand a non-scattering state; and

[0080] a pair of polarizers disposed at outer sides of a liquid crystalpanel formed by said first substrate, said second substrate and saidscattering layer,

[0081] at least one of said polarizers is formed of a circularpolarizer.

[0082] According to the present invention, optical switching between awhite representation mode and a black representation mode is achieved bya transition of state of a polymer-dispersed liquid crystal between thescattering state and the non-scattering state. Thus, there is no need ofproviding a thick planarizing film having an opening acting as anoptical window for securing a thickness for a liquid crystal layerrequired for optical switching in the transmission region, contrary tothe conventional reflection-transmission-type liquid crystal displaydevice. Further, there is no need of forming a scattering structure on aplanarized surface. Further, there is no need of forming a transparentelectrode corresponding to the optical window opening. In the presentinvention, it is sufficient to provide a reflection electrode having anoptical passage such as a slit. Thus, according to the presentinvention, the construction of the reflection-transmission-type liquidcrystal display device is significantly simplified.

[0083] Other objects and further features of the present invention willbecome apparent from the following detailed description when read inconjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0084]FIG. 1 is a diagram showing the construction of a pixel region ofa reflection-type VA-mode liquid crystal display device according to afirst embodiment of the present invention;

[0085]FIG. 2 is a diagram showing a cross-sectional structure of thereflection-type VA-mode liquid crystal display device of FIG. 1;

[0086]FIG. 3 is a diagram showing the domain structure formed in thereflection-type VA-mode liquid crystal display device of FIG. 1;

[0087]FIG. 4 is a diagram showing the construction of a comparativeexperiment of the reflection-type VA-mode liquid crystal display device;

[0088]FIG. 5 is a diagram showing an example of black representationmode in the reflection-type liquid crystal display device of FIG. 1;

[0089]FIG. 6 is a diagram showing a modification of the reflection-typeliquid crystal display device of FIG. 1;

[0090]FIG. 7 is a cross-sectional diagram showing the construction of areflection-type liquid crystal display device according to a secondembodiment of the present invention;

[0091]FIG. 8 is a diagram showing the directivity of the reflectionlight formed in the reflection-type liquid crystal display device ofFIG. 7;

[0092]FIG. 9 is a diagram showing the directivity of the reflectionlight formed in the reflection-type liquid crystal display device ofFIG. 1;

[0093]FIG. 10 is a diagram showing the cross-sectional structure of areflection-type liquid crystal display device according to a thirdembodiment of the present invention;

[0094]FIG. 11 is a diagram showing the cross-sectional structure of areflection-type liquid crystal display device according to a fourthembodiment of the present invention;

[0095]FIG. 12 is a diagram showing reflection of incident light in thereflection-type liquid crystal display device of FIG. 11;

[0096]FIGS. 13A and 13B are diagrams showing examples of refractiveindex ellipsoid respectively for the phase compensation film and liquidcrystal layer used in the reflection-type liquid crystal display deviceof FIG. 12;

[0097]FIGS. 14A and 14B are diagrams showing the cross-sections of therefractive indices ellipsoid of FIGS. 13A and 13B, respectively;

[0098]FIG. 15 is a diagram showing the azimuth dependence ofreflectivity of the reflection-type liquid crystal display device of thepresent invention in the black representation mode together with acomparative experiment;

[0099]FIG. 16 is a diagram showing the azimuth dependence of contrastratio of the reflection-type liquid crystal display device of thepresent invention together with a comparative experiment;

[0100]FIG. 17 is a diagram showing the construction of a conventionalreflection-transmission type liquid crystal display device;

[0101]FIG. 18 is a diagram showing a first construction of areflection-transmission-type liquid crystal display device according toa fifth embodiment of the present invention;

[0102]FIGS. 19A and 19B are diagrams showing the operational principleof the reflection-transmission-type liquid crystal display device ofFIG. 18;

[0103]FIG. 20 is a diagram showing a second construction of areflection-transmission-type liquid crystal display device according thefifth embodiment of the present invention;

[0104]FIGS. 21A and 21B are diagrams showing the operational principleof the reflection-transmission-type liquid crystal display device ofFIG. 20;

[0105]FIG. 22 is a diagram showing an example of a driving method usedin the fifth embodiment of the present invention;

[0106]FIG. 23 is a diagram showing another example of the driving methodused in the fifth embodiment of the present invention;

[0107]FIG. 24 is a diagram showing a further example of the drivingmethod used in the fifth embodiment of the present invention;

[0108]FIGS. 25A and 25B are diagrams showing an example of a TFTsubstrate used in the present embodiment;

[0109]FIG. 26 is a diagram showing the operational characteristics ofthe reflection-transmission-type liquid crystal display device of thepresent embodiment;

[0110]FIG. 27 is a diagram showing the construction of a color filterused in the reflection-transmission-type liquid crystal display deviceof the present embodiment;

[0111]FIG. 28 is a diagram showing another construction of the colorfilter used in the reflection-transmission-type liquid crystal displaydevice of the present invention; and

[0112]FIG. 29 is a diagram showing a further construction of the colorfilter used in the reflection-transmission-type liquid crystal displaydevice of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0113] [First Embodiment]

[0114]FIGS. 1 and 2 show respectively the plan view and across-sectional view of a reflection-type liquid crystal display device10 according to a first embodiment of the present invention for the partcorresponding to one pixel.

[0115] Referring to FIGS. 1 and 2, the reflection-type liquid crystaldisplay device 10 is basically formed of a lower glass substrate 11, anupper glass substrate 14 facing the lower glass substrate 11, and aliquid crystal layer 13 having a negative dielectric anisotropy confinedbetween the substrates 11 and 14, and the lower glass substrate 11carries thereon a TFT (thin-film transistor) 11A and further a gateelectrode 11B and a data electrode 11C cooperating with the TFT 11A. Forthe glass substrate 11, it is possible to use a conventional TFTsubstrate used in transmission-type liquid crystal display panels. Inthis case, a pixel electrode 11D of a transparent conductor such as ITOis provided on the glass substrate 11 in the state connected to the TFT11A electrically.

[0116] The TFT 11A, the gate electrode 11B and the date electrode 11Care covered by an insulating film 11E such as a resin, and a projectionand depression pattern 12 of a resist layer is provided on the foregoinginsulating film 11E, wherein the projection and depression pattern 12forms projections and depressions on the insulating film 11E.

[0117] The projection and depression pattern 12 is covered with areflection electrode 12A, wherein the reflection electrode 12A isconnected electrically to the pixel electrode 11D at the central part ofthe pixel region by way of a contact hole 11F formed in the insulatingfilm 11E.

[0118] The reflection electrode 12A forms projections and depressions incorrespondence to the projection and depression pattern 12 except forthe part thereof corresponding to the contact hole 11F, and thus, thereis formed a flat region in the pixel region at the central part thereofcorresponding to the contact hole 11F.

[0119] On the opposing substrate 14, on the other hand, there is formedan opposing electrode 14A at the side thereof facing the substrate 11uniformly and continuously, and there is formed an alignment controlstructure 12B on the opposing electrode 14A in the part thereofcorresponding to the contact hole 11F by a resin or a dielectricmaterial having a dielectric constant smaller than the dielectricconstant of the liquid crystal layer 13, for controlling the alignmentdirection of the liquid crystal molecules 13A in the liquid crystallayer 13.

[0120] Further, there is formed a vertical alignment film 12C on thesubstrate 11 so as to cover the projection and depression pattern 12 andthe reflection electrode 12A, and another vertical alignment film 12D isprovided on the substrate 14 so as to cover the opposing electrode 14Aand the alignment control structure 12B.

[0121] It should be noted that the alignment films 12C and 12D functionso as to align the liquid crystal molecules 13A in the liquid crystallayer 13 in the direction generally perpendicular to the substrate 11 or14 as illustrated in FIG. 2 by dotted lined in the non-activated stateof the pixel in which no drive electric field is applied to the liquidcrystal layer 13. On the other hand, because there is formed thealignment control structure 12B at the central part of the pixel in theliquid crystal display device 10 of FIGS. 1 and 2, the liquid crystalmolecules are tilted toward the alignment control structure 12B, and asa result, there are formed domains A-D in the pixel region asrepresented in FIG. 3 in which the liquid crystal molecules are tiltedin the direction indicated by the arrows.

[0122] Further, on the outer side of the substrate 14, there is formed aTAC (triacetate cellulose) film 15 having a retardation of about 100 nmin the thickness direction, and a phase compensation film 16 having aretadation of about ¼ of the visible wavelength and a polarizer 17 arelaminated on the TAC film 15 consecutively.

[0123] In the reflection-type liquid crystal display device 10 of FIGS.1 and 2, the environmental light incident obliquely to the polarizer 17is converted to a linear polarized light by the polarizer 17 andincident to the liquid crystal layer 13 after being converted to acircularly polarized light by the ¼-wavelength film 16.

[0124] In the non-activated state of the liquid crystal display device10 in which there is no voltage applied across the reflection electrode12A and the opposing electrode 14A, it should be noted that the liquidcrystal molecules 13A are aligned generally perpendicularly to thesubstrate 11 or 14 in the liquid crystal layer 13 as represented in FIG.2, and the circularly polarized light incident to the liquid crystallayer 13 is reflected by the reflection electrode 12A. Thereby, thereflected light passes consecutively through the liquid crystal layer13, the TAC film 15 and the ¼-wavelength film 16 consecutively in thereverse direction and is converted to a linearly polarized light havingthe polarization plane rotated by 90 degrees with regard to the initialpolarization plane. Thereby, the linearly polarized light is cut off bythe polarizer 17.

[0125] In the case a drive voltage is applied across the reflectionelectrode 12A and the opposing electrode 14A, on the other hand, theliquid crystal molecules 13A in the liquid crystal layer 13 are alignedgenerally parallel to or obliquely to the liquid crystal layer 13, andthe circularly polarized light incident to the liquid crystal layer 13through the ¼-wavelength film 16 and the TAC film 15 is converted tolinearly polarized light by the retardation of the liquid crystal layer13. The linearly polarized light thus formed is then reflected by thereflection electrode 12A and is passed through the ¼-wavelength film 16and the TAC film 15 in the reverse direction consecutively. Thereby, thereflected linearly polarized light is converted to linearly polarizedlight having a polarization plane identical with the polarization planeof the linearly polarized light converted from the incident light at thepolarizer 17, and the linearly polarized light thus obtained is exitedthrough the polarizer 17.

[0126] In the reflection-type liquid crystal display device 10 of such aconstruction, it should be noted that there is formed no projection anddepression pattern 12 in the part corresponding to the contact hole 11Fas a result of formation of the contact hole 11F in the reflectionelectrode 12A, and thus, the environmental light incident to thesubstrate 14 obliquely is not reflected back to the observer in the partof the reflection electrode 12A where the contact hole is formed.Because of this, the problem of degradation of reflectivity at thecentral part of the pixel cannot be avoided in the reflection-typeliquid crystal display device 10 having the construction of FIGS. 1 and2.

[0127] Further, optical loss caused by the alignment control structure12B cannot be avoided even though the alignment control structure 12B isformed of a transparent resin for minimizing the optical loss.

[0128] Thus, in a structure such as the one shown in FIG. 4 in which thealignment control structure 12B is formed at the central part of thepixel region and the contact hole 11F is formed in the vicinity of a TFT11C provided at the peripheral part of the pixel region, it isinevitable that there are formed plural regions of low reflectivity inthe pixel region when viewed in the direction perpendicular to thesubstrate 14. In such a structure, the brightness of the imagerepresentation is deteriorated seriously.

[0129] In the case of the liquid crystal display device 10 of FIGS. 1and 2, on the other hand, the alignment control structure 12B coincideswith the contact hole 11F when viewed in the direction perpendicularlyto the substrate 14, and the degradation of reflectivity is suppressedminimum.

[0130] Further, as can be seen from the cross-sectional view of FIG. 2,there is formed a depression in the region of the contact hole 11F incorrespondence to the projecting alignment control structure 12B, suchthat the depression has a lateral size and a width respectivelycorresponding to a lateral size and a width of the alignment controlstructure 12B. As a result, substantially the same cell thickness ismaintained also in such a region where the projecting alignment controlstructure 12B is formed.

[0131] Next, fabrication process of the reflection-type liquid crystaldisplay device 10 of FIGS. 1 and 2 will be explained.

[0132] In the present embodiment, a substrate produced for atransmission-type liquid crystal display device is used for the TFTsubstrate 11, and thus, the TFT substrate 11 carries thereon the TFT11A, the gate electrode 11B, the date electrode 11C and the transparentpixel electrode 11D. The TFT substrate 11 is then formed with a resistlayer by applying a positive resist film by a spin-coating process witha thickness of about 1.2 μm such that the positive resist film coversthe TFT 11A, the gate electrode 11B, the date electrode 11C and thetransparent pixel electrode 11D.

[0133] The resist layer thus formed has a flat surface, and ultravioletirradiation process is conducted, after applying a prebaking process at90° C. for 30 minutes, for forming the projection and depression pattern12 by using a mask, except for the central part of the pixel region, inwhich the contact hole is to be formed.

[0134] By developing the resist layer thus exposed, followed byconducting a final baking process at 200° C. for 60 minutes, theprojection and depression pattern 12 is formed.

[0135] The projection and depression pattern 12 thus formed is thencoated with an Al film by conducting an evaporation deposition process,and the reflection electrode 12A for the pixel region is formed bypatterning the Al film thus formed by applying a photolithographicprocess.

[0136] Next, formation of the alignment control structure 12B will beexplained.

[0137] First, a positive photosensitive transparent resin layer having adielectric constant of 3.2 is applied to the substrate 14 with athickness of about 1.2 μm by a spin coating process so as to cover theelectrode 14A.

[0138] Next, the resin layer thus formed is subjected to a prebakingprocess at 90° C. for 30 minutes, followed by an ultraviolet exposureprocess that uses a mask. Further, by consecutively conducting adeveloping process, a post-exposure process, a first baking process at130° C. for 2 minutes, and further a final baking process at 220° C. for6 minutes, the foregoing alignment control structure 12B is formed atthe central part of the pixel region.

[0139] Further, vertical alignment films 12C and 12D each containing aside chain diamine are applied respectively on the surface of the TFTsubstrate 11 and the opposing substrate 13 such that the verticalalignment film 12C covers the projection and depression pattern 12 andthe reflection electrode 12A and such that the vertical alignment film12D covers the electrode 14A and the alignment control structure 12B.

[0140] Next, the substrates 11 and 14 thus prepared are stacked witheach other via a spacer having a diameter of 3 μm therebetween, and aliquid crystal having a negative dielectric anisotropy (Δε=−3.5)characterized by a refractive index difference Δn between theextraordinary ray and the ordinary of 0.067 is injected into the gapformed between the substrates 11 and 14. Thereby, a liquid crystal panelof vertical alignment mode is formed.

[0141] Further, by stacking the TAC film 15, the ¼ wavelength film 16and the polarizer 17 consecutively on the outer surface of the substrate14, the fabrication process of the reflection-type liquid crystaldisplay device 10 is completed.

[0142]FIG. 5 is a diagram showing the state of the black representationmode in the liquid crystal display device 10 of the present embodimentfor the case the proportion of the vertical alignment component (sidechain diamine) in the vertical alignment films 12C and 12D with regardto the entire amine component is set to 5%, 10% and 25%.

[0143] Referring to FIG. 5, it can be seen that there is caused anextensive leakage of light in the case the proportion of the verticalalignment component in the vertical alignment film is set to 5% or 10%,and associated with such a leakage of light, there is caused the problemof degradation of contrast ratio.

[0144] On the other hand, in the case the proportion of the verticalalignment component in the alignment films 12C and 12D is 25%, it can beseen that there is little leakage of light. Thus, from the result ofFIG. 5, it is concluded that the proportion of the vertical alignmentcomponent in the vertical alignment films 12C and 12D should bepreferably set to 25% or more.

[0145] Generally, leakage of light is caused whenever the liquid crystalmolecule is tilted however small the tilt angle may be. However, it isthought that recognition of such light leakage by human beings occurswhen the tilt angle of the liquid crystal molecules has exceeded acertain threshold.

[0146] In the case of a transmission-type liquid crystal display devicein which no projections or depressions are formed on the surface, asufficient contrast ratio is achieved when the proportion of thevertical alignment component in the molecular orientation film is 5%. Onthe other hand, the result of FIG. 5 shows that a sufficient contrastratio cannot be secured in the reflection-type liquid crystal displaydevice unless the proportion of the vertical alignment component in thealignment film is set to be 25% or more.

[0147] Table 1 below explains the reflectivity (brightness) and contrastratio obtained for the white representation mode in the reflection-typeliquid crystal display device 10 as viewed in the directionperpendicular to the liquid crystal panel, in comparison with the resultfor the reflection-type liquid crystal display devices according tocomparative experiments 1 and 2 (Comparative 1, Comparative 2), whereinthe measurement of Table 1 is conducted by using an integrating sphereoptical source. In the comparative experiment 1, on the other hand, thereflection-type liquid crystal display device uses an oblique slit inthe opposing electrode 14A in place of the alignment control structure12B while in the comparative experiment 2, the reflection-type liquidcrystal display device uses an alignment control structure similar tothe alignment control structure 12B on the substrate 14 but with aheight of 2.0 μm. TABLE 1 VA component % brightness % contrastEmbodiment 1 5 13 2.6 10 13 11.0 25 13 23.0 50 13 23.3 Comparative 1 5010 17.7 Comparative 2 50 12 21.2

[0148] Referring to Table 1, it can be seen that the reflection-typeliquid crystal display device 10 of the present embodiment achievesbrightness superior to the liquid crystal display device of any of thecomparative experiments 1 and 2, although the proportion of the verticalalignment component (side chain diamine) with regard to the totaldiamine component is changed in the range of 5-50% in the presentembodiment. Further, it can be seen that a contrast ratio of 23.0 ormore is achieved by setting the proportion of the vertical alignmentcomponent to be 25% or more.

[0149] Considering the fact that a TN-mode reflection-type liquidcrystal display device can provide brightness of only about 13% andcontrast ration of 18 in the maximum, it will be understood that thereflection-type liquid crystal display device 10 of the presentembodiment can provide much superior performance as compared with such aTN-mode reflection-type liquid crystal display device.

[0150] In Table 1, it is noted that the brightness of the whiterepresentation mode is reduced by about 30% in the case of thereflection-type liquid crystal display device of the comparativeexperiment 1 over the reflection-type liquid crystal display device 10of the present embodiment. It is believed that this result is caused bythe effect that the liquid crystal molecules in the vicinity of the slitformed in the opposing electrode does not cause switching.

[0151] In the comparative experiment 2, it is also noted that theachieved brightness is smaller than the brightness achieved by thepresent embodiment by about 8%. It is believed that this has been causedas a result of reduced retardation of the liquid crystal layer in thepart located on the alignment structure. It should be noted that thealignment structure in the comparative experiment 2 is has a heightlarger than the alignment structure used in the present embodiment.

[0152] In the reflection-type liquid crystal display device 10 of thepresent embodiment, it is also possible to form an alignment controlstructure 12B, in the case a material having a dielectric constantlarger than the dielectric constant of the liquid crystal layer 13 isused for the alignment control structure 12B, such that the alignmentcontrol structure 12B fills the depression formed on the side of the TFTsubstrate 11 in correspondence to the conductive plug 11F as representedin FIG. 6. According to such a construction, it is also possible torealize the molecular alignment of the liquid crystal molecules tiltingtoward the center of the pixel region.

[0153] [Second Embodiment]

[0154] Next, explanation will be made on a reflection-type liquidcrystal display device 20 according to a second embodiment of thepresent invention.

[0155]FIG. 7 shows the construction of the reflection-type liquidcrystal display device 20 wherein those parts corresponding to the partsdescribed previously are designated by the same reference numerals andthe description thereof will be omitted.

[0156] Referring to FIG. 7, the reflection-type liquid crystal displaydevice 20 has a construction somewhat similar to that of thereflection-type liquid crystal display device 10 explained previously,except that the alignment control structure 12B is removed from thesubstrate 11 or 14.

[0157] Instead, there are formed polymer chains 13B having anorientation in the liquid crystal layer 13 in the liquid crystal displaydevice 20 of the present embodiment, wherein the polymer chains 13Bfunction so as to cause tilting of the liquid crystal molecules 13Atoward the central part of the pixel region. In FIG. 7, it should benoted that the reference numeral 13B merely represents the polymerchains schematically and is not intended to depict the actual structureof the polymer chains or indicate individual polymer chains.

[0158] In more detail, the projection and depression pattern 12 isformed on the TFT substrate 11 in the present embodiment in the form ofan elongated pattern such that each projection pattern extends in thelongitudinal direction or lateral direction of the substrate asrepresented in FIG. 8. Further, the alignment films 12C and 12D areformed by using a vertical alignment film containing the verticalalignment component with a proportion of 25%.

[0159] Referring to FIG. 8, the projections and depressions in theprojection and depression pattern 12 are formed in each of the domainregions A-D schematically represented in FIG. 3, wherein each of theprojections or depressions extends in the longitudinal direction orlateral direction along the outer peripheral edge of the regions A-D.

[0160] Further, the substrate 11 and the substrate 12 are stacked witheach other via a spacer having a diameter of 3 μm, and a liquid crystaladmixed with a resin forming a polymer chain upon ultravioletirradiation is injected into the gap formed between the substrates 11and 14. The liquid crystal may contain the resin with a proportion of0.3% by weight.

[0161] With this, the liquid crystal layer 13 is formed. In the presentembodiment, a resin that causes photo-polymerization upon irradiation ofultraviolet radiation (I-line) with the intensity of 2000 mJ/cm² or moreis used.

[0162] In the reflection-type liquid crystal display device thus formed,it will be noted that the intensity of the reflection light formed bythe projections and depressions in the projection and depression pattern12 increases in the longitudinal direction and in the lateral directionof the substrate as represented in FIG. 8, by forming the laterally orlongitudinally elongating projection and depressions on the TFTsubstrate 11. In the projection and depression pattern 12 of FIG. 1, onthe other hand, no such a directivity appears in the reflected light asrepresented in FIG. 9.

[0163] Thus, in the present embodiment, a drive voltage of 4V is appliedto the liquid crystal display device thus obtained, and ultravioletradiation is applied to the substrate 14 in this state such that theintensity of the reflected light, reflected by the projection anddepression pattern 12 becomes 2000 mJ/cm² or more in the liquid crystallayer 13 in the longitudinal direction and in the lateral direction. Asa result of the action of the reflected light formed from theultraviolet radiation in the longitudinal direction and lateraldirection, there are formed polymer chains 13B in the liquid crystallayer 13 extending in the longitudinal and lateral directions of thesubstrate, and the liquid crystal molecules 13A in the liquid crystallayer 13 are aligned as represented in FIG. 2 as a result of the actionof the vertical alignment films 12C and 12D and further the polymerchains 13B thus formed.

[0164] The measurement of brightness and contrast ratio conducted on thereflection-type liquid crystal display device thus formed revealedsimilar results as in the case of the reflection-type liquid crystaldisplay device 10 of the previous embodiment.

[0165] According to the present embodiment, it is possible to polymerizea photo-polymerizable compound in an arbitrary direction in which theoptical intensity becomes maximum, by controlling the shape of theprojection and depression pattern 12 reflecting the ultravioletradiation and by incorporating the photo-polymerizable compound into theliquid crystal layer 13.

[0166] [Third Embodiment]

[0167]FIG. 10 shows the construction of a reflection-type liquid crystaldisplay device 30 according to a third embodiment of the presentinvention, wherein those parts corresponding to the parts describedpreviously are designated by the same reference numerals and thedescription thereof will be omitted.

[0168] Referring to FIG. 10, the liquid crystal display device has aconstruction mixing the features of the first embodiment and the secondembodiment in that the glass substrate 14 carries thereon the alignmentcontrol structure 12B and that the projections in the projection anddepression pattern 12 have an elongated form extending in thelongitudinal or lateral direction of the substrate as represented inFIG. 8. Further, the liquid crystal layer 13 includes therein theoptically polymerized chains 13B.

[0169] In the liquid crystal display device 30 of FIG. 10, it should benoted that the absorption axis of the polarizer 17 is set in thelongitudinal direction of the substrate and the direction of theretardation axis of the ¼ wavelength film 16 is set to form an angle of45 degrees with respect to the absorption axis of the polarizer 17.

[0170] Table 2 below compares the brightness and contrast ratio obtainedfor the reflection-type liquid crystal display device 30 thus obtainedin the white representation mode with the brightness and contrast ratioobtained for a similar reflection-type liquid crystal display device(comparative example 3: Comparative 3), in which the direction of theabsorption axis of the polarizer 17 is offset from the longitudinaldirection of the substrate by 45 degrees. TABLE 2 VA component %brightness % contrast Embodiment 3 25 13 24.8 Comparative 3 25 13 23.0

[0171] Referring to Table 2, it will be noted that there is nosubstantial change with regard to brightness between the presentembodiment and the comparative experiment, while it will also be notedthat there is an improvement of contrast ratio in the liquid crystaldisplay device of the present embodiment.

[0172] It is believed that this improvement is achieved as a result ofimprovement of the black representation mode, which in turn is caused asa result of setting the absorption axis of the polarizer 17 in thedirection in which the reflection intensity of the projection anddepression pattern 12 becomes maximum.

[0173] [Fourth Embodiment]

[0174]FIG. 11 shows the construction of a reflection-type liquid crystaldisplay device 40 according to a fourth embodiment of the presentinvention while FIG. 12 shows the propagation of rays in thereflection-type liquid crystal display device 40 of FIG. 11. In FIG. 12,it should be noted that only those parts related to the optical pathlength of the optical rays is represented and representation of otherparts are omitted.

[0175] Referring to FIG. 11, the liquid crystal display device 40 of thepresent embodiment is generally formed of a lower glass substrate 41, anupper glass substrate 44 facing the lower glass substrate 41 and aliquid crystal layer 43 having a negative dielectric anisotropy confinedbetween the upper and lower glass substrates 41 and 44, wherein thelower glass substrate 44 carries thereon elements such as a TFT notillustrated, a gate electrode 41C cooperating with the TFT, and furthera data electrode not illustrated. A standard TFT substrate designed fora transmission-type liquid crystal display device can be used for theglass substrate 44. In this case, a pixel electrode 41D of a transparentconductor such as ITO is formed on the glass substrate 41 in the stateconnected to the TFT electrically.

[0176] It should be noted that the TFT, the gate electrode 41C and thedate electrode are covered by an insulating film such as a resin, andthere is formed a projection and depression pattern 42 on the insulatingfilm 41E by patterning and processing a resist film.

[0177] The projection and depression pattern 42 is covered by areflection electrode 42A of Al and the like, and the reflectionelectrode is connected to the pixel electrode 41D via a contact hole 41Fformed in the insulation film 41E preferably at the central part of thepixel region.

[0178] On the upper glass substrate 44, there is formed an opposingelectrode 44A uniformly and continuously at the surface of the substrate44 facing the substrate 41.

[0179] Further, there is formed a vertical alignment film 42C on thesubstrate 41 so as to cover the projection and depression pattern 42 andthe reflection electrode 42A and another vertical alignment film 42D isformed on the substrate 44 so as to cover the opposing electrode 44A.

[0180] In the non-activated state in which there is no drive electricfield applied to the liquid crystal layer 43, the alignment films 42Cand 42D act to align the liquid crystal molecules in the directiongenerally perpendicular to the substrate 41 or 44, while the liquidcrystal molecules contacting the projection and depression pattern 42cause tilting as represented in FIG. 12 because of the existence of theprojection and depression pattern 42.

[0181] Further, a phase compensation film 45 preferably formed of a TACfilm is formed on the outer side of the substrate 44, and a ¼ wavelengthfilm 46 and a polarizer 47 are laminated consecutively further on thecompensation film 45.

[0182] In the reflection-type liquid crystal display device 40 of thepresent embodiment, it should be noted that the liquid crystal molecules43A constituting the liquid crystal layer 43 is not limited to the onehaving a negative dielectric anisotropy but also may be the one having apositive dielectric anisotropy. Even in such a case, the liquid crystaldisplay device 40 is a reflection-type liquid crystal display devicebecause of the fact that the liquid crystal molecules 43A are aligned inthe direction generally perpendicular to the plane of the substrate 41or 44 in the non-activated state thereof.

[0183] In the reflection-type VA-mode liquid crystal display devices10-30 explained in the preceding embodiments, it should be noted thatthe liquid crystal layer 13 shows a retardation also in thenon-activated state of the device in view of the fact that theenvironmental light impinges obliquely to the liquid crystal layer 13and in view of the fact that the liquid crystal molecules 13A are tiltedby the projection and depression pattern 42. Thus, the desired idealblack representation cannot be achieved in the non-activated state ofthe foregoing reflection-type VA-mode liquid crystal display device,unless the retardation of the liquid crystal layer 13 in thenon-activated state is compensated for by the phase compensation filmand the like.

[0184] In the case of a transmission-type VA-mode liquid crystal displaydevice, there is already a proposal of the technology for compensatingfor the retardation of a vertically aligned liquid crystal layer byusing a phase compensation film in the British Patent 1462978 or in theJapanese Laid-Open Patent Publication 10-153802.

[0185] In these proposals, the retardation of a phase compensation filmgiven as df·{(n_(x)+n_(y))/2−n_(z)} is set to be generally equal to theretardation of the liquid crystal layer defined as dlc·Δn, wherein dfrepresents the thickness of the phase compensation film, n_(x), n_(y)and n_(z) respectively represent the refractive indices of the phaseretardation film in the x-, y- and z-directions, dlc represents thethickness of the liquid crystal layer, and Δn represents the refractiveindex difference between the extraordinary ray and the ordinary ray inthe liquid crystal layer.

[0186] In such a technology of transmission-type VA-mode liquid crystaldisplay device, the phase compensation film is used merely for blockingthe light incident obliquely in the black representation mode and forimproving the viewing angle, and the desired compensation of the blackrepresentation mode is not attained when applied to a reflection-typeVA-mode liquid crystal display device.

[0187] It should be noted that a reflection-type VA-mode liquid crystaldisplay device having projections and depressions on a reflectionsurface is designed so as to incorporate as much environmental light aspossible and reflect the incorporated environmental light toward theobserver.

[0188] Referring to FIG. 12, the environmental light incident obliquelywith an incident angle θ1 is refracted with a refraction angle θ2determined by the refractive index ratio between the air and the phasecompensation film and impinges into the liquid crystal layer 43 with anincident angle θ3.

[0189] At the interface between the liquid crystal layer 43 and thesubstrate 44, the liquid crystal molecules 43A are controlled thealignment state thereof by the vertical alignment film 42D notillustrated in FIG. 12 in the direction generally perpendicular to theplane of the substrate 44. Because of this, the incident light hits theliquid crystal molecule 43A with the angle of θ3 in the vicinity of theinterface between the liquid crystal layer 43 and the substrate 44.Here, it should be noted that the refractive index of the liquid crystallayer is about 1.5 and is approximately identical to the refractiveindex of the phase compensation film 45. Because of this, it is possibleto regard that the incident angle θ3 is nearly equal to the incidentangle θ2.

[0190] On the other hand, in such a reflection-type VA-mode liquidcrystal display device, it is necessary to emit the obliquely incidentenvironmental light in the direction perpendicularly to the substrate 44as explained with reference to preceding embodiments, and for thispurpose, there is formed the projection and depression pattern 42 on theTFT substrate 41.

[0191] In FIG. 12, such a projection and depression pattern 42 isapproximated by a cone having a cross-section of an isosceles triangle.Thus, on the projection and depression pattern 42, the liquid crystalmolecules 43A are aligned perpendicularly to the oblique edge of thetriangle that forms an angle with regard to the plane of the substrate41 as a result of the function of the vertical alignment film 42Ccovering the projection and depression pattern 42.

[0192] Thus, in the liquid crystal layer 43, the liquid crystalmolecules 43A increases the tilt angle gradually in the thicknessdirection of the liquid crystal layer 43 from the value of 0 at theinterface between the liquid crystal layer 43 and the substrate 44 tothe value of ζ at the interface between the liquid crystal layer 43 andthe projection and depression pattern 42. Thus, in the vicinity of theinterface between the liquid crystal layer 43 and the substrate 41, theincident angle of the light impinging to the liquid crystal molecule 43Ais decreased from the foregoing angle θ3 by the angle ζ because of thetilt caused in the liquid crystal molecule 43A by the projection anddepression pattern 43A.

[0193] Thus, the incident light entering into the liquid crystal layer43 from the phase compensation film 45 hits the projection anddepression pattern 42 with an incident angle ζ and reflected also with areflection angle ζ. As a result, the reflected light again hits theliquid crystal molecule 43A aligned perpendicularly on the projectionand depression pattern 42 with an incident angle ζ.

[0194] At the interface between the liquid crystal layer 43 and thesubstrate 41, the alignment direction of the liquid crystal molecules iscontrolled perpendicularly to the plane of the substrate 41. Thus, theliquid crystal molecules 43A change the alignment direction in thethickness direction of the liquid crystal layer 43 gradually from thesubstrate 41 to the substrate 44. Associated with this, the incidentangle of the reflection light incident to the liquid crystal molecules43A is reduced gradually and becomes zero at the interface to thesubstrate 44.

[0195] In the optical system of FIG. 12, the optical path length withinthe phase compensation film 45 in the first half part of the opticalpath, defined as the optical path of the incident light reaching theprojection and depression pattern 42, is given as dv/cos θ2, whereinthis optical path length is approximated to be equal to dv/cos 2 in viewof the relationship θ2≈θ3 (dv/cos θ2≈dv/cos 2 ζ). Further, the opticalpath length of the incident light in the liquid crystal layer 13 isgiven as dlc/cos 2 ζ. On the other hand, the optical path length of thereflection light reflected vertically to the principal plane of thesubstrate 41 by the projection and depression pattern 42 is given as dlcin the liquid crystal layer and dv in the phase compensation film 45.

[0196] Thus, in the case of the reflection-type VA-mode liquid crystaldisplay device 40 in which the environmental light enters obliquely, itwill be noted that there is caused a retardation even in thenon-activated state of the liquid crystal display device because of thedifferent optical path lengths between the incoming optical path andoutgoing optical path, and that the magnitude of the retardation dependson the incident angle θ1 and the angle ζ of the projection anddepression pattern 42.

[0197] In an example in which the liquid crystal layer 43 has athickness dlc of 3 μm and a refractive index difference Δn of 0.067 andin which the projection and depression pattern 42 provides an averageinclination angle <ζ> of 13 degrees, the retardation of the liquidcrystal layer 43 in the non-activated state in which no drive voltage isapplied to the liquid crystal display device is calculated to be 33 nmas represented in Case A of Table 3 below, provided that the incidentangle θ1 of the incident light is set to 25 degrees. TABLE 3 retardationof liquid crystal phase reflector <ζ> layer difference {circle over (1)}compensation A 13.06 33.25 15.26 45.9% B 8.98 15.98 9.05 56.6% C 7.6713.01 7.92 60.9% D 7.48 11.87 7.53 63.4% reflector phase difference{circle over (2)} compensation A 29.65  89.2% B 16.15 101.1% C 13.71105.4% D 12.85 108.3% reflector phase difference {circle over (3)}compensation A 36.32 109.2% B 19.04 119.1% C 15.94 122.5% D 14.82 124.9%reflector phase difference {circle over (4)} compensation A 51.34 154.4%B 25.96 162.5% C 21.42 164.6% D 19.76 166.5%

[0198] In Table 3, it should be noted that Cases B, C and D are cited inaddition to Case A, wherein Case B represents the case in which theaverage inclination angle <ζ> is set to 9 degrees, Case C represents thecase in which the average inclination angle <ζ> is set to 7.7 degrees,and Case D represents the case in which the average inclination angle<ζ> is set to 7.5 degrees.

[0199] In order to compensate for such retardation caused obliquely inthe liquid crystal layer 43, it is possible to use a film having anegative dielectric anisotropy in the direction perpendicular to thesubstrate.

[0200] Thus, Table 1 further shows the retadation value in the obliquedirection and the efficiency of compensation for those cases in whichthe phase compensation film 45 has a refractive index difference{(n_(x)+n_(y))/2−n_(z)} of 0.0006 (phase difference {circle over (1)}),0.0013 (phase difference {circle over (2)}), 0.0017 (phase difference{circle over (3)}) and 0.0024 (phase difference {circle over (4)}).

[0201] Next, compensation of the oblique retardation achieved by usingsuch a phase compensation film 45 having a negative dielectricanisotropy will be explained.

[0202]FIG. 13A shows a refractive index ellipsoid of the phasecompensation film 45 having a negative dielectric anisotropy in thevertical direction of the substrate while FIG. 13B shows a refractiveindex ellipsoid of the liquid crystal layer 43 that has a positivedielectric anisotropy. Further, FIG. 14A shows a cross-section of therefractive index ellipsoid of FIG. 13A taken in the Y-Z plane, whileFIG. 14B shows a cross-section of the refractive index ellipsoid of FIG.13B taken in the Y-Z plane. In the discussion hereinafter, it is assumedthat there is no in-plane anisotropy in any of the phase compensationfilm 45 and the liquid crystal layer 43 (n_(x)=n_(y)).

[0203] Referring to FIGS. 13A and 13B and further with reference toFIGS. 14A and 14B, it will be noted that the refractive indices of theordinary ray and extraordinary ray of the light incident to an X-Y planewith an incident angle θ correspond to the major axis and the minor axisin the case of the phase compensation film 45 and to the minor axis andthe major axis in the case of the liquid crystal layer 43, of an ellipsethat formed at the cross section of the refractive index ellipsoidsectioned by a plane

[0204] Referring to FIGS. 14A and 14B, the apparent refractive indicesny′ and nz′ respectively representing the refractive indices in the Y-and Z-directions for the case the incident light has impinged with anangle θ with respect to the normal direction of the substrate(Z-direction), are obtained according to the following equations.$\begin{matrix}{{\frac{Y^{2}}{n_{y}^{2}} + \frac{Z^{2}}{n_{z}^{2}}} = 1} \\{{\frac{n_{y}^{\prime 2}\quad \cos^{2}\quad \theta}{n_{y}^{2}} + \frac{n_{y}^{\prime 2}\quad \sin^{2}\quad \theta}{n_{z}^{2}}} = 1} \\{n_{y}^{\prime 2} = \frac{1}{\frac{\cos^{2}\quad \theta}{n_{y}^{2}} + \frac{\sin^{2}\quad \theta}{n_{z}^{2}}}} \\{n_{y}^{2} = {\frac{n_{y}n_{z}}{\sqrt{{n_{z}^{2}\quad \cos^{2}\quad \theta} + {n_{y}^{2}\quad \sin^{2}\quad \theta}}} = {\frac{n_{z}}{\sqrt{{\frac{n_{z}^{2}}{n_{y}^{2}}\cos^{2}\quad \theta} + \left( {1 - {\cos^{2}\quad \theta}} \right)}} = \frac{n_{z}}{\sqrt{1 - {\upsilon \quad \cos^{2}\quad \theta}}}}}} \\{wherein} \\{\upsilon = {\frac{n_{y}^{2} - n_{z}^{2}}{n_{y}^{2}}.}} \\{{\frac{Y^{2}}{n_{y}^{2}} + \frac{Z^{2}}{n_{z}^{2}}} = 1} \\{{\frac{n_{z}^{\prime 2}\quad \sin^{2}\quad \theta}{n_{y}^{2}} + \frac{n_{z}^{\prime 2}\quad \cos^{2}\quad \theta}{n_{z}^{2}}} = 1} \\{n_{z}^{\prime 2} = \frac{1}{\frac{\sin^{2}\quad \theta}{n_{y}^{2}} + \frac{\cos^{2}\quad \theta}{n_{z}^{2}}}} \\{n_{z}^{2} = {\frac{n_{y}n_{z}}{\sqrt{{n_{z}^{2}\quad \sin^{2}\quad \theta} + {n_{y}^{2}\quad \cos^{2}\quad \theta}}} = \frac{n_{z}}{\sqrt{{\frac{n_{z}^{2}}{n_{y}^{2}}\left( {1 - {\cos^{2}\quad \theta}} \right)} + {\cos^{2}\quad \theta}}}}} \\{\quad {= {\frac{n_{z}}{\sqrt{\frac{n_{z}^{2}}{n_{y}^{2}} - {\upsilon \quad \cos^{2}\quad \theta}}}.}}}\end{matrix}$

[0205] The retardation values of the liquid crystal layer and the phasecompensation film and the values of the efficiency of compensationrepresented in Table 3 above were calculated based on the apparentrefractive indices n_(x)′, n_(y)′ and n_(z)′ as well as the incidentangle θ, and thus, incorporates the effect of oblique path of theincident light.

[0206] Referring to Table 3 again, it can be seen that the phasecompensation films {circle over (1)} and {circle over (4)} cannotprovide sufficient compensation, while the phase compensation films{circle over (2)} and {circle over (3)} can provide near 100%compensation.

[0207] It should be noted that such compensation of retardation changeswith the retardation dlc An of the liquid crystal layer, and thus, theretardation compensation has to be changed when the retardation of theliquid crystal layer is changed.

[0208] Generally, the value of retardation is represented by the valuein the direction parallel to or perpendicular to the substrate. Thus, itis preferable to represent the retardation of the phase compensationfilm also in terms of the value parallel to or perpendicular to thesubstrate, not by the value oblique to the substrate.

[0209] Thus, the preferable retardation value obtained as noted above isrepresented for the case of the reflector A having the averageinclination angle ζ of 13 degrees as

0.5≦[df·{(n _(x) +n _(y))/2−n _(z)}]/(dlc·Δn)≦0.7.

[0210] Within this range, a conspicuous effect is achieved for thecompensation of black representation mode, although there can be a casein which the retardation compensation deviates by about 10% from theoptimum value.

[0211] In the case of using the reflectors B-D having the averageinclination angle ζ of 7-9 degrees, on the other hand, the liquidcrystal layer 43 has a retardation in the range of 11-16 nm in thenon-activated state. In such a case, the phase compensation film {circleover (2)} provides the best result. In this case, the preferable rangeof retardation of the phase compensation film is determined as

0.4≦[df·{(n _(x) +n _(y))/2−n _(z)}]/(dlc·Δn)≦0.6,

[0212] including the allowable margin from the optimum value.

[0213] Summarizing the foregoing results, it is concluded that thepreferable retardation range of the phase compensation film 45 for thereflection-type liquid crystal display device 40 is determined in therange of

0.4≦[df·{(n _(x) +n _(y))/2−n _(z)}]/(dlc·Δn)≦0.7.

[0214] When the inclination angle ζ has decreased below about 7 degrees,the incident angle θ1 for incorporating the environmental light becomestoo small and it becomes difficult to incorporate the environmentallight.

[0215] In the construction of FIG. 11, it is particularly advantageousto use a TAC film having a retardation of about 10 nm in the in-planedirection and about 50 nm in the normal direction for the phasecompensation film 45. With this, substantially ideal black modecompensation is achieved with low cost.

[0216] It should be noted that the polarizer 47 generally has amoisture-blocking film of TAC but such a TAC film is disposed betweenthe ¼ wavelength film 46 and the polarizer 47. Thus, no compensationeffect comparable to the one achieved by the phase compensation film 45can be obtained by such a moisture resistance film. This point will benoted later.

[0217] In the liquid crystal display device 40 of FIG. 11, the ¼wavelength film 45 is disposed between the phase compensation film 45and the polarizer 47, wherein such a ¼-wavelength film shows smallerwavelength dispersion as compared with the liquid crystal layer 43.

[0218] Thus, by disposing such a phase compensation film of smallwavelength dispersion between the polarizer 47 and the liquid crystallayer 43 and by achieving a 90-degree rotation of the polarizationplane, it is possible to realize excellent black mode representationcharacterized by small wavelength dispersion and hence small leakage ofvisible light.

[0219] By doing so, it is not preferable to dispose the ¼-wavelengthfilm 46, in other words, a second phase compensation film, outside thephase compensation film 45 or a first phase compensation film. It shouldbe noted that the refractive index ellipsoid of the phase compensationfilm 45 has an azimuth dependence, and the construction that disposesthe ¼-wavelength film 46 between the phase compensation film 45 and theliquid crystal layer 43 would results in a situation in which thelinearly polarized light passed through the polarizer is compensated. Inthis case, there can be a problem that a satisfactory compensation isachieved in a specific azimuth angle while no such a satisfactorycompensation is achieved in other azimuth angle. Thereby, the overallcompensation effect is reduced.

[0220] In the case the ¼-wavelength film 46 is formed outside the phasecompensation film 45, the phase compensation film 45 compensates for theoptical phase of the circularly polarized light passed through the¼-wavelength film 46, and the effect of the azimuth dependence iseliminated. It should be noted that circularly polarized light isequivalent in all the azimuth directions, and thus, the opticalcompensation is achieved for all the azimuth directions in this case,even when there is an azimuth dependence on the refractive indexellipsoid of the phase compensation film 45.

[0221] Meanwhile, a phase compensation film such as a TAC film 45 has anin-plane retardation axis. Thus, there is caused a problem in that theretardation of the ¼-wavelength film 46 is affected when such a TAC film45 is laminated with the ¼-wavelength film 46. In the case the¼-wavelength film 46 and the phase compensation film 45 are laminated inthe state that respective retardation axes coincide each other, forexample, the retardation value of such a laminated structure in thein-plane direction becomes the sum of the retardation values of thephase compensation film 45 and the ¼-wavelength film 46. In the casethey are disposed such that respective retardation axes cross with eachother perpendicularly, the retardation becomes the difference betweenthe retardation values of the phase compensation film 45 and the¼-wavelength film 46.

[0222] Thus, in the case an element formed of lamination of a½-wavelength film and a ¼-wavelength film is used for the ¼-wavelengthfilm 46 for minimizing the wavelength dispersion, there arises a problemthat the phase compensation film 45 is included in the laminatedstructure in the case the in-plane retardation axis of the phasecompensation film 45 is offset from the in-plane retardation axis of the¼-wavelength film 46. Thereby, there can be a possibility that thewavelength dispersion characteristic is affected.

[0223] In order to avoid this problem, it is preferable to coincide thein-plane retardation axis of the TAC film forming the phase compensationfilm 45 with the in-plane retardation axis of the ½-wavelength film or¼-wavelength film constituting the laminated ¼-wavelength film 46. Inthis case, there is caused no effect other than increase or decrease ofthe retardation.

[0224] Particularly, it is possible to achieve complete compensation ofthe black representation by disposing the phase compensation film 45 andthe ¼ wavelength film 46 in such a relationship that respective in-planeretardation axes extend parallel with each other and that the sum of thein-plane retardation becomes almost ¼ of the visible wavelength. Bydoing so, it is possible to suppress the deviation of retardation of the¼-wavlelength film 46 caused by the in-plane retardation of the¼-wavelength film 46.

[0225] Especially, in the case the ¼-wavelength film 46 is an element oflaminated structure as noted before, it is sufficient to align thein-plane retardation axis of the phase compensation film 45 with thein-plane retardation axis of any of the ¼ wavelength film or the ½wavelength film. Further, adjustment of retardation is conducted suchthat the sum of the in-plane retardation of the ¼-wavelength film andthe phase compensation film 45 becomes equal to ¼ wavelength or suchthat the sum of the in-plane retardation of the ½-wavelength film andthe phase compensation film 45 becomes equal to ½ wavelength. In thiscase, it is not always true that the sum of the in-plane retardation ofthe phase compensation film 45 and the laminated ¼-wavelength film 46becomes equal to ¼ of the visible wavelength. However, a similar effectis achieved when the retardation of one of the phase compensation filmsin the laminated ¼-wavelength film 46 is adjusted such that thelaminated ¼-wavelength film 46 as a whole provides the in-planeretardation equal to ¼ of the visible wavelength.

[0226] Next, the fabrication process of the reflection-type liquidcrystal display 40 of FIG. 11 will be explained.

[0227] In the present embodiment, a resist film is applied on the TFTsubstrate 41 by a spin coating process with a thickness of about 1 μmand a prebaking process is conducted at 90° C. for 30 minutes.Thereafter, the resist film thus formed is exposed to ultravioletradiation while using a mask corresponding to the projection anddepression pattern. By developing the resist film after exposure,followed by a baking process at 135° C. for 40 minutes and a finalbaking process at 200° C. for 60 minutes, the projection and depressionpattern 42 is formed with the average inclination angle <ζ> of 7.7degrees. It should be noted that this inclination angle is changedarbitrarily by changing the baking temperature and the baking time.

[0228] Further, an Al film 42A is deposited on the surface of theprojection and depression pattern 42 thus formed by an evaporationdeposition process with a thickness of 200 nm.

[0229] Further, the vertical alignment molecular orientation films 42Cand 42D are applied to the TFT substrate 41 thus processed and also tothe opposing substrate 44, and the substrates 41 and 44 thus processedare assembled together via intervening spacers each having a diameter of3 μm, and a vacant panel is obtained.

[0230] Next, a liquid crystal having a negative dielectric anisotropy(Δε=−3.5) and a refractive index difference Δn of 0.067 between theextraordinary ray and the ordinary ray is injected into the gap formedbetween the foregoing substrates 41 and 42. With this, a liquid crystalpanel is obtained.

[0231] Next, two biaxial TAC films having an in-plane retardation of 10nm and a normal direction retardation of 47 nm are laminated on thesubstrate 44 as the phase compensation film 45 such that the in-planeretardation axis has an azimuth angle of 85 degrees, and a ¼-wavelengthfilm having an in-plane retardation of 135 nm and a ½-wavelength filmhaving an in-plane retardation of 250 nm are laminated consecutivelywith the azimuth angle of the retardation axes set to 140 degrees and 85degrees, respectively. Thereby, the laminated ¼-wavelength film 46 isformed. Further, the polarizer 47 is formed on the ¼-wavelength film 46such that the absorption axis is oriented in the azimuth direction of 75degrees.

[0232] In the VA-mode reflection-type liquid crystal display device 40thus formed, it is possible to suppress the wavelength dispersion byusing the laminated ¼-wavelength film as the ¼-wavelength film 46.Further, by setting the direction of the in-plane retardation axis ofthe phase compensation film 45 to be coincident to the in-planeretardation axis of the ½-wavelength film constituting the laminated¼-wavelength film 46, the value of the in-plane retardation of the½-wavelength film is reduced by the amount of the in-plane retardationof the phase compensation film 45, and the ¼-wavelength film 46 as awhole shows an in-plane retardation value corresponding to ½ wavelengthat the green wavelength (540 nm), in which the sensitivity of human eyeis largest.

[0233] On the other hand, the phase compensation film 45 is a filmhaving a negative dielectric anisotropy for compensating for theretardation of the liquid crystal layer in the state the electric fieldis applied, wherein the phase compensation film 45 has an in-planeretardation df·{(n_(x)+n_(y))/2−n_(z)} satisfying the relationship of

df·{(n _(x) +n _(y))/2−n _(z)}/(dlc·Δn)=0.47

[0234] with respect to the in-plane retardation dlc·Δn of the liquidcrystal layer 43.

[0235] Table 4 below shows the result of measurement of reflectivity ofthe reflection-type liquid crystal display device 40 thus obtained foreach of the white representation mode and black representation mode byapplying a predetermined drive voltage. The measurement of Table 4 wasmade by using a spectrometer that uses an integrating sphere opticalsource (Embodiment 4). It should be noted that an integrating sphereoptical source is a diffusive optical source emitting light in allangles and all the azimuth directions and can provide illumination closeto the environmental light such as interior lighting or sunlight. TABLE4 reflectivity orientation black white contrast Embodiment 4 VA 0.5312.64 24.1 Comparative4 VA 0.68 12.66 18.6 Comparative5 VA 0.66 12.5518.9 Comparative6 VA 0.71 12.74 18.1 Comparative7 horizontal 0.71 12.8618.0

[0236] Referring to Table 4, it can be seen that the reflection-typeliquid crystal display device 40 of the present embodiment can achievethe reflectivity of 0.53 at the black representation mode and thereflectivity of 12.64 in the white representation mode. With this, acontrast ratio of 24.1 is realized.

[0237] In Table 4, the results of comparative experiments 4-7(Comparative 4-Comparative 7) are also listed.

[0238] In the comparative experiment 4, the order to the phasecompensation film 45 and the laminated ¼-wavelength film 46 is reversed,and thus, the substrate 44 is first covered with the ¼-wavelength filmof the laminated ¼-wavelength film 46, next with the ½-wavelength filmof the laminated ¼-wavelength film 46, and finally the phase retardationfilm 45 on the foregoing ½-wavelength film. Otherwise, the constructionof the liquid crystal display device of the comparative experiment 4 isidentical with the one used in Embodiment 4.

[0239] In the comparative experiment 5, on the other hand, a liquidcrystal display device similar to the one used in Embodiment 4 is usedexcept that the ½-wavelength film constituting the upper layer of thelaminated ¼-wavelength film 46 is replaced with a uniaxial film havingan in-plane retardation of 270 nm. Further, the ¼-wavelength film in thelaminated ¼-wavelength film 46 is disposed such that the retardationaxis op the ¼-wavelength film is coincident to the anchoring orientation(rubbing orientation) of the liquid crystal layer. With this, thein-plane retardation is reduced by 20 nm as compared with the¼-wavelength film of Embodiment 4.

[0240] In the comparative experiment 6, on the other hand, the phasecompensation film 45 of the liquid crystal display device of Embodiment4 is eliminated Further, an uniaxial film having an in-plane retardationof 270 nm is used for the ½ wavelength film constituting a part of thelaminated ¼-wavelength film.

[0241] In the comparative experiment 7, on the other hand, a horizontalalignment film is applied to the substrates 41 and 44, and thesubstrates 41 and 44 are assembled with each other via spacers having adiameter of 3 μm. Further, a liquid crystal having a positive dielectricanisotropy (Δε=6.0) and a refractive index difference Δn between theextraordinary ray and the ordinary ray of 0.067 is confined in the gapformed between the substrates 41 and 44. Thus, the liquid crystaldisplay device of the comparative experiment is a reflection-type liquidcrystal display device of TN-mode.

[0242] Referring to Table 4 again, it will be noted that the liquidcrystal display device of the present embodiment provides a reflectivitylower than any other liquid crystal display devices of the comparativeexperiments in the black representation mode, and as a result, a highestcontrast ratio is achieved by the liquid crystal display device ofEmbodiment 4.

[0243]FIGS. 15 and 16 show the reflectivity and contrast ratio of theblack representation mode for the VA-mode reflection-type liquid crystaldisplay device 40 according to the present embodiment (Embodiment 4) forthe case the liquid crystal display device 40 is illuminated with a spotlight source with an incident angle of 25 degrees, wherein FIG. 15 showsthe reflectivity while FIG. 16 shows the contrast ratio. Further, FIGS.15 and 16 show the result of similar measurement with regard to theapparatus of the comparative experiment 6.

[0244] Referring to FIGS. 15 and 16, it can be seen that the black modereflectivity is reduced in the reflection-type liquid crystal displaydevice 40 of the present embodiment over the liquid crystal displaydevice of the comparative experiment for the entire azimuth angles andimprovement of contrast ratio is achieved.

[0245] Generally, there is a tendency that the reflectivity in the blackrepresentation mode becomes minimum in the reflection-type liquidcrystal display device having a single polarizer in the azimuthdirection corresponding to the absorption axis of the polarizer andmaximum in the azimuth direction corresponding to the transmission axis.

[0246] In FIGS. 15 and 16, too, it can be seen that the reflectivity inthe black representation mode takes a minimum value at the azimuth anglenear 255 degrees corresponding to the absorption axis of the polarizer47 and that a maximum contrast ratio is achieved in this azimuth angle.

[0247] Table 5 below shows the reflectivity of the black representationmode and white representation mode as well as the azimuth dependence ofthe contrast ratio for the liquid crystal display device 40 ofEmbodiment 4 in the direction of the absorption axis of the polarizer incomparison with the liquid crystal display device of the comparativeexperiment 6. TABLE 5 reflectivity mode black white contrast Embodiment4 VA 0.36 24.10 67.5 Comparative 6 VA 0.44 21.47 48.7

[0248] Referring to Table 5, it can be seen that the reflectivity of theblack representation mode is reduced by 18% in the present embodiment ascompared with the comparative experiment in the azimuth angle of about255 degrees corresponding to the direction of the absorption axis of thepolarizer. Further, Table 5 indicates that the contrast ratio hasincreased in this azimuth angle from 48.7% to 67.5%.

[0249] [Fifth Embodiment]

[0250] Next, description will be made on a reflection-transmission-typeliquid crystal display device according to a fifth embodiment of thepresent invention.

[0251]FIG. 17 shows the general construction of a conventionalreflection-transmission-type liquid crystal display device.

[0252] Referring to FIG. 17, the reflection-transmission-type liquidcrystal display device 50 is basically formed of a pair of glasssubstrates 51 and 52 and a liquid crystal layer 53 confinedtherebetween, wherein a transparent electrode 52A is formed on the innersurface of the glass substrate 52 uniformly. On the other hand, there isformed a planarization film 51A on the inner surface of the glasssubstrate 51 and, an opening 51 a is formed in the planarization film51A as an optical transmission window.

[0253] On the surface of the planarization film 51A, there is formed areflection electrode 51B having projections and depressions, and atransparent electrode 51C is formed on the substrate 51 incorrespondence to the foregoing opening 51 a.

[0254] Further, there is formed a circular polarizer 54 on the outerside of the substrate 51 and another circular polarizer 55 is formed onthe outer side of the substrate 52.

[0255] In the reflection-transmission type liquid crystal display device50, in which optical switching is achieved by modulating the retardationof the liquid crystal layer 53, it is necessary to set the optical pathlength of the light in the liquid crystal layer 53 incident theretothrough the glass substrate 52 and exit therefrom after being reflectedby the reflection electrode 51B to be equal to the optical path lengthof the light that enters the liquid crystal layer 53 from the substrate51 through the optical window 51 a and exits after passing through theliquid crystal layer 53 and the glass substrate 52. This means that itis necessary to form the planarization film 51A to have a thickness of ½the thickness of the liquid crystal layer 53.

[0256] However, fabrication of such a liquid crystal display device iscomplex in view of the need of the steps of forming the thickplanarization film 51A on the substrate 51, forming the reflectionelectrode 51B on the planarization film 51A, forming the optical window51 a and forming a transparent electrode 51C on the substrate 51 incorrespondence to the optical window 51 a, in addition to ordinarymanufacturing steps for fabricating a liquid crystal display device.Thus, the liquid crystal display device 50 of the conventionalreflection-transmission-type suffers from the problem of increased cost.

[0257] Further, in the reflection-transmission-type liquid crystaldisplay device 50 of FIG. 17, there arises the need of forming a barriermetal film 51 b at the interface between the Al reflection electrode 51Band the transparent electrode 51C of ITO for preventing corrosion causedby electrolytic effect.

[0258]FIG. 18, on the other hand, shows the construction of areflection-transmission-type liquid crystal display device 60 accordingto a fifth embodiment of the present invention that eliminates theforegoing problems.

[0259] Referring to FIG. 18, the liquid crystal display device 60 isbasically formed of a pair of glass substrates 61 and 62 and a polymernetwork liquid crystal layer 63 confined therebetween, wherein atransparent electrode 62A is formed uniformly on the inner surface ofthe glass substrate 62.

[0260] On the inner surface of the glass substrate 61, there is formed areflection electrode pattern 61A having a slit-shape opening 61 a, andthe liquid crystal layer 63 takes an optically transparent state in thenon-activated state of the liquid crystal display device in which nodrive voltage is applied to the liquid crystal layer 63. In theactivated state in which a driving electric field is applied to theliquid crystal layer 63, on the other hand, the liquid crystal layer 63takes a scattering state. Such a liquid crystal layer 63 may be realizedy using a polymer network liquid crystal disclosed for example in theJapanese Laid-Open Patent Publication 5-27228.

[0261] Further, a circular polarizer 64 is provided on the outer side ofthe glass substrate 61 and a linear polarizer 65 is provided on theouter side of the glass substrate 62.

[0262]FIGS. 19A and 19B are diagrams explaining the operation of thereflection-transmission-type liquid crystal display device 60 of FIG. 18in the black representation mode and white representation mode,respectively.

[0263] Referring to FIG. 19A, the left side of the drawing shows thereflection-mode operation while the right side shows thetransmission-mode operation, wherein it will be noted that the incidentlight from the front side of the liquid crystal panel is converted intolinearly polarized light in the reflection mode operation by the linearpolarizer 65 and is converted further into circularly polarized light bythe liquid crystal layer 63 of non-scattering state. It should be notedthat the liquid crystal layer 63 has a retardation of about ¼ wavelengthof the incident light and has a retardation axis forming an angle of 45degrees with respect to the absorption axis of the polarizer 65. Here,it should be noted that the retardation of the liquid crystal layer 63in the non-scattering state is by no means limited to ¼ of the incidentlight wavelength λ or visible wavelength but may have the value of(0.5n+¼)λ; n=0, 1, 2 . . . n, wherein n is a natural number.

[0264] The incident light thus converted to circularly polarized lightis then reflected by the reflection electrode 61A in the state of thecircularly polarized light and is converted to linear polarized lighthaving a polarization plane crossing the initial polarization planeperpendicularly. The reflected light having such a linearly polarizedstate and exiting the liquid crystal layer 63 is then cut off by thelinear polarizer 65, and the desired black representation is obtained.

[0265] In the transmission-mode operation, the incident light incidentto the substrate 61 from the backside of the liquid crystal panel isconverted circularly polarized light upon passage through the circularpolarizer 64 and is introduced into the liquid crystal layer 63 throughthe optical window 61 a in the reflection electrode 61A.

[0266] As the liquid crystal layer 63 is in the non-scattering state,the incoming circularly polarized light is converted to linearlypolarized light having a polarization plane crossing the absorption axisof the linear polarizer 65 upon passage through the liquid crystal layer63 similarly to the case of the reflected circularly polarized lightexplained above, and the transmission light passed through the liquidcrystal layer 63 is cut off also by the linear polarizer 65.

[0267] In the white representation mode of FIG. 19B, on the other hand,the liquid crystal layer 63 is in the scattering state and the linearlypolarized light passed though the linear polarizer 65 and incident tothe liquid crystal layer 63 is scattered and the scattered light isreflected by the reflection electrode 61A. It should be noted that suchscattered light undergoes further scattering upon passage through theliquid crystal layer 63 in the reverse direction after reflection, andas a result, the linear polarizer 65 receives the light includingtherein various polarization components of various polarization planesin addition to the polarization component having a polarization planeparallel to the absorption axis thereof.

[0268] Thus, the polarization component having a polarization planecrossing the absorption axis passes through the polarizer 65 in the formof linearly polarized light, and a desired white representation isobtained.

[0269] The same explanation applied also to the case of the transmissionlight. Thus, the incident light incident to the substrate 61 through thecircularly polarized light is scattered at the liquid crystal layer 63,and those polarization components formed as a result of the scatteringand having a polarization plane crossing the absorption axis of thepolarizer 65 passes through the polarizer 65.

[0270] In the reflection-transmission-type liquid crystal display deviceof such a construction, there is no need of forming the thickplanarization film 51A or electrode 51B carrying a scattering structure,or a transparent electrode 51C corresponding to the optical window 51 a.It is sufficient to merely form the reflection electrode 61A patternedto form a slit on the inner surface of the substrate 61. Further, itshould be noted that the reflection electrode 61A does not make acontact with the transparent electrode, and thus, there is no need offorming a barrier metal layer.

[0271] Thus, the fabrication process of the liquid crystal displaydevice of the present embodiment is easy to produce and the fabricationcost is reduced significantly.

[0272] Further, it should be noted that the liquid crystal displaydevice that uses the transition of state of the liquid crystal layerbetween the non-scattering state and scattering state has no problem oflimited viewing angle, and excellent viewing angle characteristics canbe achieved.

[0273] In the example of FIG. 18, it should be noted that the liquidcrystal layer has a retardation value of ¼ wavelength of the incidentlight in the non-scattering state. On the other hand, it is alsopossible to use a liquid crystal layer having a very small retardationas represented in FIG. 20, wherein it should be noted that FIG. 20 showsa liquid crystal display device 70 according to a modification of thepresent embodiment. In FIG. 20, those parts corresponding to the partsdescribed previously are designated by the same reference numerals andthe description thereof will be omitted.

[0274] Referring to FIG. 20, a polymer dispersion liquid crystal layer73 having a very small in-plane retardation in the non-scattering stateis used in the reflection-type liquid crystal display device 70 in placeof the liquid crystal layer 63. The liquid crystal layer 73 has anin-plane retardation smaller than the product Δn·d of the liquid crystalused for the scattering layer wherein Δn represents the birefringenceand d represents the cell thickness. It is thereby preferable to set thein-plane retardation negligible in the liquid crystal layer 73.Associated with this, the linearly polarized light is replaced by acircular polarizer 66.

[0275]FIGS. 21A and 21B show the operation of thereflection-transmission-type liquid crystal display device 70 of FIG. 20respectively in the black representation mode and white representationmode.

[0276] Referring to FIG. 21A, the left side of the drawing shows thereflection mode operation it the black representation mode, while theright drawing shows the transmission mode operation. Thus, in thereflection mode, the incoming light from the front side of the liquidcrystal panel is converted to circularly polarized light by the circularpolarizer 66, wherein the circularly polarized light thus formed passesthrough the liquid crystal layer 73 in the state of the circularlypolarized light in view of the ignorable small retardation of the liquidcrystal layer. The liquid crystal layer is in the non-scattering state.

[0277] The incident light thus passed through the liquid crystal layer73 is reflected by the reflection electrode 61A in the circularlypolarized state and passes through the liquid crystal layer 73 in thereverse direction while maintaining the circularly polarized state. Thecircularly polarized light thus passed through the liquid crystal layer73 enters into the circular polarizer 66 in the reverse direction and iscut off.

[0278] In the transmission mode operation, on the other hand, theincoming light incident to the substrate 61 from the backside isconverted to circularly polarized light by the circular polarizer 64 andis introduced into the liquid crystal layer 73 through the opticalwindow 61 a in the reflection electrode 61A.

[0279] As the liquid crystal layer 73 is in the non-scattering state,the incident circularly polarized light passes through the liquidcrystal layer 73 while maintaining the circularly polarized state and iscut off by the circular polarizer 66 similarly to the reflectedcircularly polarized light explained above.

[0280] In the white representation state of FIG. 19B, the liquid crystallayer 73 is in the scattering state, and thus, the circularly polarizedlight incident to the liquid crystal layer 73 experiences scattering inthe liquid crystal layer 73. The scattered incident light is thenreflected by the reflection electrode 61A and experiences furtherscattering as it is propagated through the liquid crystal layer 73 inthe reverse direction. As a result, the circular polarizer 66 at thefront side receives various polarization components having variouspolarization planes.

[0281] Thus, the component having a polarization plane perpendicular tothe absorption axis passes through the polarizer 66 and the desiredwhite representation is achieved.

[0282] The same situation hold true also in the case of the transmissionlight in that the incoming light incident to the substrate 61 from thebackside through the circular polarized light 64 is scattered in theliquid crystal layer 73, and the polarization component formed as aresult of the scattering and having a polarization plane crossing theabsorption axis of the polarizer 66 passes through the polarizer 66.

[0283] In the reflection-transmission-type liquid crystal display device70 of such a construction, there is no need of forming the thickplanarization film 51A or electrode 51B carrying a scattering structurethereon, or a transparent electrode 51C corresponding to the opticalwindow 51 a, contrary to the conventional reflection-transmission-typeliquid crystal display device 70, and it is sufficient to form thereflection electrode 61A patterned according to the slit shape on theinner surface of the substrate 61. Further, it will be noted that thereflection electrode 61A does not make a contact with the transparentelectrode, and thus, there is no need of forming a barrier metal layer.Thus, the fabrication process is simplified and the cost of the liquidcrystal display device is reduced significantly.

[0284] In such a liquid crystal display device that uses transition ofstate of the liquid crystal layer between the non-scattering state andthe scattering state, there arises no problem of limited viewing angle,and excellent viewing angle characteristics can be achieved.

[0285] Table 6 below compares the fabrication process of theconventional reflection-transmission-type liquid crystal display device50 of FIG. 17 and the reflection-transmission-type liquid crystaldisplay device 70 or 70 of the present invention. TABLE 6 ConventionalPresent invention planarization necessary not necessary film surfacenecessary not necessary scattering structure transparent necessary notnecessary electrode reflection necessary necessary electrode

[0286] Referring to Table 6, it will be noted that the present inventioncan eliminate the step of forming the planarization film 51A, the stepof forming the projection and depression pattern 51B on theplanarization film 51A and further the step of forming the transparentelectrode 51C on the optical window.

[0287] Thus, in the present invention, it is sufficient to merelypattern the reflection electrode and the fabrication process of thereflection-transmission-type liquid crystal display device is simplifiedsubstantially.

[0288] Meanwhile, in the reflection-transmission-type liquid crystaldisplay device 60 of FIG. 18 or in the in thereflection-transmission-type liquid crystal display device 70 of FIG.20, in which a uniform electrode is formed on a front substrate and aslit-shape electrode pattern is formed on the rear substrate, there areseveral possible driving modes for applying a driving electric field tothe liquid crystal layer 63 as represented in FIGS. 22-24.

[0289]FIG. 22 is a so-called lateral electric field mode or IPS mode anda drive voltage is applied across a pair of mutually adjacent electrodefingers of the interdigital electrode constituting the reflectionelectrode.

[0290]FIG. 23, on the other hand, shows a driving mode designated hereinas vertical electric field mode or S mode for distinction from the IPSmode, wherein a drive electric voltage is applied between the opposingelectric field 62 and the reflection electric field 61A.

[0291] Further, FIG. 24 shows a driving mode designated hereinafter asone-side vertical electric field mode or sS mode in which the IPS modeand the S mode noted above are combined. Thus, in the driving mode ofFIG. 24, the opposing electrode 62 and one of the electrode fingers aredriven to a first voltage level and the electrode fingers at both sidesare driven to a second drive voltage.

[0292]FIG. 25A shows an example of the construction of the reflectionelectrode 61A used in the S driving mode of FIG. 23, while FIG. 25Bshows the construction of the reflection electrode 61A used in the IPSdriving mode of FIG. 22 or sS driving mode of FIG. 24.

[0293] Referring to FIG. 25A, there is formed a TFT 61T, a gateelectrode 61G and a data electrode 61D on the glass substrate 61, and anelectrode having a slit in corresponding to the transmission region 61 ais formed as the reflection electrode 61A.

[0294] In the construction of FIG. 25B, on the other hand, pluralityinterdigital electrodes 61A₁ and 61A₂ are formed on the glass substrate61 alternately in addition to the TFT 61T, gate electrode 61G and thedata electrode 61D, wherein the interdigital electrode 61A2 is connectedto a common line 61C. Further, there is formed a gap between theelectrode 61A₁ and the electrode 61A₂ in correspondence to thetransmission region 61 a.

[0295] By using the TFT substrate of FIG. 25A or FIG. 25B for thesubstrate 61 and assembling the substrates 61 and 62 together via aspacer having a diameter of 5 μm, liquid crystal display devices havingthe construction of the liquid crystal display device 60 of FIG. 18 havebeen manufactured respectively for testing the IPS driving mode, Sdriving mode and the sS driving mode. Thereby, a horizontal alignmentfilm is formed on each of the substrates 61 and 62, and the alignmentfilm is subjected to a rubbing process such that the liquid crystalmolecules cause a homogeneous alignment in the direction perpendicularto the slit direction.

[0296] Further, a liquid crystal mixture of a UV-curable liquid crystaland a liquid crystal having a birefringence Δn of 0.2306 and adielectric anisotropy Δε of 15.1 is confined into the gap formed betweenthe substrates 61 and 62. Further, by conducting ultravioletirradiation, a polymer network scattering layer is formed in the liquidcrystal layer 63.

[0297]FIG. 26 shows the relationship between the applied drive voltageand the transmittance for the reflection-transmission-type liquidcrystal display device 60 thus formed for the case the width E of theelectrode pattern 61A is set to 4 μm and the width G of the slit 61 a ischanged variously. In FIG. 26, it should be noted that the electrodewidth E and the slit width G are represented in terms of microns.Further, the transmittance is normalized by the transmittance in thenon-activated state.

[0298] Referring to FIG. 26, it will be noted that the drive voltage isreduced with reducing slit width G and that a minimum drive voltage isachieved in the case of using the S driving mode.

[0299] In another experiment of the present embodiment, a liquid crystaldisplay device having the construction of FIG. 18 is formed by using theTFT substrate of the construction shown in FIG. 25A or 25B.

[0300] In this experiment, a horizontal alignment film is formed on thesurface of the substrate 61 or opposing substrate 62 by a PVA film or asoluble polyimide film. After applying a rubbing process to thealignment film for causing a homogenous alignment in the liquid crystalmolecules, the substrates 61 and 62 are assembled together withintervening spacers each having a diameter of 2.3 μm, and a liquidcrystal mixture containing a nematic liquid crystal having abirefringence Δn of 0.067 added with a UV-curable liquid crystalcontaining a polymerization starter with a proportion of 10 weight % isintroduced into the gap formed between the substrates 61 and 62.

[0301] Further, by applying ultraviolet radiation to the liquid crystalpanel thus formed, there is formed a polymer network liquid crystalhaving a retardation of 154 nm.

[0302] Further, a linear polarizer 65 is provided on the outer side ofthe substrate 62 such that the transmission axis of the polarizer 65 isoriented with an angle of about 45 degrees from the direction ofalignment of the liquid crystals. Further, a circular polarizer 64 isprovided at the outer side of the substrate 61.

[0303] Thus, it becomes possible to produce thereflection-transmission-type liquid crystal display device 60 with lowcost.

[0304] In another experiment, the reflection-transmission-type liquidcrystal display device 70 of FIG. 20 is manufactured by using a TFTsubstrate having a construction of FIG. 25A or 25B for the TFT substrate61.

[0305] In this experiment, the substrate 61 and the opposing substrate62 are assembled together via intervening spacers having a diameter of 6μm, and a liquid crystal mixture containing a liquid crystal having abirefringence Δn of 0.23 added with a UV-curable resin monomer with aproportion of 20 weight %, is introduced into the gap formed between thesubstrates 61 and 62. By applying ultraviolet irradiation to the liquidcrystal layer thus formed, the polymer-dispersed liquid crystal layer 73is obtained.

[0306] By providing the circular polarizers 64 and 66 at respectiveouter sides of the TFT substrate 61 and the opposing substrate 62, thereflection-transmission-type liquid crystal display device 70 thatprovides the white representation mode in the non-activated state whereno drive voltage is applied and the black representation mode in theactivated state, is obtained.

[0307] In a further experiment, the reflection-transmission-type liquidcrystal display device 70 of FIG. 20 is formed by using a TFT substrateof the construction shown in FIG. 25A or 25B for the substrate 61.

[0308] In this experiment, a vertical alignment film of PVA or solublepolyimide is formed on the surface of the substrates 61 and 62, and thesubstrates 61 and 62 are assembled together via spacers having adiameter of 5 μm. Further, a liquid crystal mixture containing a liquidcrystal having a birefringence Δn of 0.23 added with a UV-curable resincontaining a polymerization starter with a proportion of 10 weight % isintroduced into the gap formed between the substrates 61 and 62, and thepolymer network liquid crystal layer 73 is obtained by applyingultraviolet irradiation.

[0309] The reflection-transmission-type liquid crystal display device 70is then completed, by providing the circular polarizers 64 and 66 atrespective outer sides of the TFT substrate 61 and the opposingsubstrate 62, wherein the liquid crystal display device 70 thus formedprovides the black representation mode in the non-activated state inwhich no drive voltage is applied and the white representation mode inthe activated state.

[0310]FIG. 27 shows an example of providing a color filter CF to any ofthe reflection-transmission-type liquid crystal display device 60 ofFIG. 18 or the reflection-transmission-type liquid crystal displaydevice 70 of FIG. 20.

[0311] Referring to FIG. 27, it will be noted that the light incidentthrough the substrate 62 from the front direction and reflected by thereflecting electrode 61A is passed through the color filter CF twice,while the light incident from the backside through the TFT substrate 61passes through the color filter CF only once.

[0312] Thus, in the case the color filter CF has a uniform color purity,there arises a problem in that the color purity of the reflected lightand the color purity of the transmission light may be difference.

[0313] Thus, in the construction of FIG. 27, a part CF₁ of the colorfilter CF corresponding to the transmission region 61 a is formed tohave a thickness twice as large as the remaining part of the colorfilter CF such that both the transmission light and the reflection lighthas the same color purity.

[0314]FIG. 28 shows a modification of FIG. 27, wherein it will be notedthat the color filter CF is formed on the substrate 61 and the thicknessof the color filter CF is adjusted by using the reflection electrode61F.

[0315] Thus, by forming the color filter CF on the substrate 61 with athickness twice as large as that of the reflection electrode 61A, itbecomes possible to set the thickness of the color filter CF for thepart located on the transmission region 61 a to be twice as large as thethickness of the color filter CF on the electrode 61A. In theconstruction of FIG. 29, such an adjustment of thickness of the colorfilter CF is achieved in a self-aligned manner, and there is no need ofany patterning process.

[0316]FIG. 29 shows a modification of FIG. 28 in which there is formed apattern 61B underneath the reflection electrode 61A by a resist film orthe like, in conformity with the reflection electrode 61A.

[0317] According to such a construction, the reflection electrode 61A isformed at an elevated position on the substrate 61 as compared with thecase of FIG. 28. It should be noted that the construction of FIG. 29 iseffective particularly when the thickness of the reflection electrode61A is small and coloring of the reflection light can be achievedsufficiently in the construction of FIG. 28.

[0318] Further, the present invention is not limited to the embodimentsexplained heretofore, but various variations and modifications may bemade without departing from the scope of the invention.

What is claimed is:
 1. A reflection-type liquid crystal display device,comprising: a first substrate; a second substrate disposed so as to facesaid first substrate, said second substrate carrying projections anddepressions thereon; a reflective electrode provided on said secondsubstrate so as to cover said projections and depressions in electricalcontact with a switching device provided on said second substrate via acontact hole; and a liquid crystal layer provided between said first andsecond substrates, said liquid crystal layer having a negativedielectric anisotropy, wherein said contact hole is disposed centrallyto said reflection electrode, and wherein a structure controllingalignment of liquid crystal molecules in said liquid crystal layer isdisposed so as to overlap said contact hole when said second substrateis viewed in a direction perpendicular thereto.
 2. A reflection-typeliquid crystal display device as claimed in claim 1, wherein saidstructure is provided on said reflection electrode.
 3. A reflection-typeliquid crystal display device as claimed in claim 1, wherein saidstructure is provided on a surface of said first substrate facing saidsecond substrate.
 4. A reflection-type liquid crystal display device asclaimed in claim 1, wherein said structure has a size generally equal toa size of said contact hole when viewed in a direction perpendicular tosaud second substrate.
 5. A reflection-type liquid crystal displaydevice as claimed in claim 1, wherein said structure has a heightcorresponding to a step height formed in said reflection electrode bysaid contact hole.
 6. A method of fabricating a reflection-type liquidcrystal display device comprising a first substrate, a second substrateprovided so as to face said first substrate, said second substratecarrying thereon projections and depressions having a reflectivity, aliquid crystal layer having a negative dielectric anisotropy providedbetween said first and second substrates, and an optically polymerizedpolymer structure provided between said first and second substrates,said method comprising the steps of: causing optical polymerization of acompound constituting said polymer structure by irradiating lightperpendicularly to said second substrate and causing reflection of saidlight by said projections and depressions in an in-plane direction ofsaid second substrate; said step of causing optical polymerization isconducted by providing an in-plane directivity to the light reflected bysaid projections and depressions by a optimizing a shape of saidprojections and depressions, such that said optical polymerization isconducted in a direction corresponding to said in-plane directivity. 7.A reflection-type liquid crystal display device, comprising: a firstsubstrate; a second substrate disposed so as to face said firstsubstrate; a liquid crystal layer having a negative dielectricanisotropy disposed between said first and second substrates; and avertical alignment film formed on a surface of said first substrate anda surface of said second substrate, wherein said alignment film containsa vertical alignment component with a proportion of 25% or more withregard to total diamine components.
 8. A reflection-type liquid crystaldisplay device, comprising: a first substrate; a second substratedisposed so as to face said second substrate, said second substratecarrying thereon projections and depressions having a reflectivity; aliquid crystal layer having a negative dielectric anisotropy disposedbetween said first and second substrates; and a polarizer disposed at anouter side of said first substrate such that an absorption axis of saidpolarizer extends generally parallel to a direction in which areflection intensity caused by said projections and depressions becomesmaximum.
 9. A reflection-type liquid crystal display device, comprising:a first substrate; a second substrate disposed so as to face said firstsubstrate, said second substrate carrying projections and depressionshaving a reflectivity; a liquid crystal layer having any of positive ornegative dielectric anisotropy provided between said first and secondsubstrates; and a polarizer disposed at an outer side of said firstsubstrate, an optical phase compensation film disposed between saidfirst substrate and said polarizer, said optical phase compensation filmhaving a negative dielectric anisotropy in a direction perpendicular toa plane of said first substrate, said optical phase compensation filmhaving a retardation df{(n_(x)+n_(y))/2−n_(z)} so as to satisfy therelationship 0.4≦[df{(n _(x) +n _(y))/2−n _(z)}]/(dlcΔn)≦−0.7, whereinn_(x), n_(y) and n_(z) are refractive indices of said optical phasecompensation film respectively in an x-direction, a y-direction and az-direction, dlc is the thickness of said liquid crystal layer, and Anis a refractive index difference between an extraordinary ray and anordinary ray in the liquid crystal layer.
 10. A reflection-type liquidcrystal display device as claimed in claim 9, wherein said optical phasecompensation film has a retardation axis in a direction parallel to saidfirst substrate.
 11. A reflection-type liquid crystal display device asclaimed in claim 9, further comprising, between said polarizer and saidoptical phase compensation film, another optical phase compensation filmhaving a positive dielectric anisotropy in the direction parallel to aplane of said first substrate, said another optical phase compensationfilm having a retardation of about ¼ of the wavelength of visible light.12. A reflection-type liquid crystal display device as claimed in claim11, wherein said optical phase compensation film and said anotheroptical phase compensation film have a retardation axis in a directionparallel to said first substrate.
 13. A reflection-type liquid crystaldisplay device as claimed in claim 12, wherein said optical phasecompensation film and said another optical phase compensation film haverespective retardations such that a sum of said retardation of saidoptical phase compensation film and said retardation of said anotheroptical phase compensation film is equal to about ¼ of the wavelength ofvisible light.
 14. A reflection-transmission-type liquid crystal displaydevice, comprising: a first substrate; a second substrate provided so asto face said first substrate; a transparent electrode provided on asurface of said first substrate facing said second substrate; areflection electrode provided on a surface of said second substratefacing said first substrate, said reflection electrode having anopening; a scattering layer provided between said first and secondsubstrates, said scattering layer including therein a liquid crystallayer and changing an optical state thereof between a scattering stateand a non-scattering state; and a pair of polarizers disposed at outersides of a liquid crystal panel formed by said first substrate, saidsecond substrate and said scattering layer, at least one of saidpolarizers is formed of a circular polarizer.
 15. Areflection-transmission-type liquid crystal display device as claimed inclaim 14, wherein each of said pair of polarizers is formed of acircular polarizer.
 16. A reflection-transmission-type liquid crystaldisplay device as claimed in claim 14, wherein one of said pair ofpolarizers is a linear polarizer.
 17. A reflection-transmission-typeliquid crystal display device as claimed in claim 14, wherein saidscattering layer has a retardation of (0.5n+¼)λ, where λ is thewavelength of visible light and n is a natural number in saidnon-scattering state thereof
 18. A reflection-transmission-type liquidcrystal display device as claimed in claim 14, wherein said scatteringlayer has an in-plane retardation in said non-scattering state thereofsuch that said in-plane retardation is smaller than a product Δn·d,where Δn is the birefringence of a liquid crystal layer constitutingsaid scattering layer and d is the thickness of said liquid crystallayer.
 19. A reflection-transmission-type liquid crystal display deviceas claimed in claim 14, wherein said reflection electrode has a slitshape.
 20. A reflection-transmission-type liquid crystal display deviceas claimed in claim 14, wherein any of said first and second substratescarries a color filter, said color filter having a reflection regioncorresponding to said reflection electrode and a transmission regioncorresponding to said transmission region, said color filter havingdifferent color purities in said reflection region and in saidtransmission region.
 21. A reflection-transmission-type liquid crystaldisplay device as claimed in claim 20, wherein said color filter isprovided on said reflection electrode.